THE  LIBRARY 

OF 

THE  UNIVERSITY 
OF  CALIFORNIA 

Education 

IN  MEMORY  OF 

Professor 

George  D«  Louderback 
1874-1957 


BEGINNERS'  HAND-BOOK 


OF 


CHEMISTRY. 

THE   SUBJECT 

DEVELOPED   BY   FACTS   AND   PRINCIPLES   DRAWN   CHIEFLY 
FROM  THE  NON-METALS. 


BY 

JOHN  HOWARD  APPLETON,  A.M., 

Professor  of  Chemistry  in  Brown  University^ 
AUTHOR  OF 

THE   YOUNG   CHEMIST,"    "QUALITATIVE    CHEMICAL    ANALYSIS,"    "QUANTITATIVE 
CHEMICAL  ANALYSIS,"  "THE  LABORATORY  YEAR-BOOK." 


NEW  YORK: 

CHAUTAUQUA    PRESS, 

C.  L.  3.  G;  DEPARTMENT,  805  BROADWAY. 

1888. 


"V^OFJK^    0|S   j^HEMI^TRY 


BY 


PROFESSOR  APPLETON. 


I.  The  Young  Chemist.  A  book  of  Chemical  experiments  for  be- 
ginners in  Chemistry.  It  is  composed  almost  entirely  of  experiments, 
those  being  chosen  that  may  be  performed  with  very  simple  apparatus. 

II..  Qualitative  Analysis.  A  brief  but  thorough  manual  for  labora- 
tory use. 

It  gives  full  explanations  and  many  chemical  equations.  The  processes 
of  analysis  are  clearly  stated,  and  the  whole  subject  is  handled  in  a  manner 
that  has  been  highly  commended. 

III.  Quantitative  Analysis.     The  treatment  of  the  subject  is  such  as 
to  afford  an  acquaintance  with  the  best  methods  of  determining  all  the 
principal  elements,  as  well  as  with  the  most  important  type-processes  both 
of  gravimetric  and  volumetric  analysis. 

THE  EXPLANATIONS  ARE  DIRECT  AND  CLEAR,  so  that  a  pupil  is  enabled 
to  work  intelligently  even  without  the  constant  guidance  of  the  teacher. 
By  this  means  the  book  is  adapted  for  self-instruction  of  teachers  and 
others  who  require  this  kind  of  help  to  enable  them  to  advance  beyond 
their  present  attainments. 

IV.  The  Laboratory  Year-Book.     An  annual  publication  contain- 
ing many  convenient  tables  for  laboratory  use.     New  tables  are  constantly 
introduced,  and  changes  are  made  in^rder  to  keep  the  matter  abreast  of 
the  latest  discoveries. 


GIFT 


Copyright,  1884,  by  JOHN  HOWARD  APPLETON. 


$230 


PREFACE. 


|HIS  book   has  been    prepared  as  a  popular  intro- 
duction to  the  study  of  chemistry. 

It  is  probably  needless  to  recommend  the  sub- 
ject. Chemistry  is  recognized  as  a  science  of  such 
general  interest,  such   wide  usefulness,  and  such    universal 
application,  that  no  intelligent  person  can   endure  long  to 
remain  ignorant  of  its  principal  facts  and  laws. 

This  book  treats  principally  of  the  non-metals;  it  is  believed 
to  be  the  verdict  of  authors  and  teachers  of  experience  that 
these  furnish  the  most  suitable  material  for  a  beginner  in  the 
study  of  chemistry  ;  these  best  present  the  fundamental  facts 
and  principles  of  the  science,  and  they  do  it  in  connection 
with  objects  and  phenomena  easily  accessible  to  almost  every 
civilized  human  being. 

The  author  contemplates  the  preparation  hereafter  of  a 
book  of  similar  general  character,  only  having  its  principal 
facts  drawn  from  the  chemistry  of  the  metals. 

In  writing  this  book  it  has  been  the  effort  to  treat  the 
subject  in  a  style  that  shall  be  attractive  to  the  general  reader ; 
but  it  is  believed  that  in  no  case  has  scientific  fact  been  sacri- 
ficed in  the  interest  of  popular  form. 

The  arrangement  of  matter  in  the  book  is  in  accordance 
with  the  following  plan  :  After  the  introductory  chapters, 
which  present  the  general  principles  of  chemical  action,  the 
chief  non-metals  are  treated  in  a  scientific  order  as  follows  :  the 
monads,  hydrogen,  chlorine,  bromine,  iodine,  and  fluorine; 

980 


PREFACE. 


then  the  dyads,  oxygen  and  sulphur;  next  the  triads,  boron, 
nitrogen,  phosphorus;  finally  the  tetrads,  carbon  and  silicon; 
thus  including  the  four  great  groups  into  which  the  non- 
metals  are  naturally  arranged. 

The  historical  and  biographical  sketches,  that  are  distrib- 
uted through  the  book,  have  been  introduced  with  the  view 
of  legitimately  helping  to  retain  the  reader's  attention.  Most 
of  the  experiments  described  are  such  as  may  be  performed 
by  any  one  possessed  of  reasonable  skill ;  it  is  believed  that 
they  will  afford  profitable  instruction  as  well  as  entertain- 
ment. Allusions  to  the  applications  of  chemistry  to  the  affairs 
of  every-day  life  have  been  carefully  introduced,  and  have 
been  developed  as  fully  as  the  circumstances  seem  to 
warrant. 

Perhaps  it  is  not  improper  to  make  allusion  to  the  read- 
ing references  found  at  the  end  of  nearly  every  chapter. 
They  are  largely  from  periodical  publications,  and  it  is 
thought  that  they  will  be  of  service,  especially  to  mature 
students.  Guides  to  reading  are  now  viewed  as  among  the 
most  important  helps  offered  by  teachers  to  students.  The 
reading  lists  in  this  book  point  out  some  papers  which  are 
selected  as  being  chiefly  popular  in  style  ;  if  these  lead  the 
reader  to  consult  the  others  he  will  find  himself  introduced 
to  some  of  the  most  important  contributions  to  the  knowledge 
of  our  science. 

The  present  edition  differs  from  the  preceding  one  in  the 
addition  of  several  new  chapters.  Throughout  the  book  also 
newly-discovered  facts  have  been  introduced  in  their  proper 
places. 

BROWN  UNIVERSITY,  1888. 


CONTENTS. 


CHAPTER  I.  P*« 

BRANCHES  OP  NATURAL  SCIENCE.— The  General  Term  Science.— Scientific 

Treatment  of  a  Subject.— Province  of  Chemistry 7-9 

CHAPTER  II. 

THE  SCOPE  OP  CHEMISTRY.— The  Great  Number  of  Different  Substances  in 

the  Earth.— How  it  Happened  that  there  is  such  a  variety 10-13 

CHAPTER  III. 
THE  ELEMENTARY  SUBSTANCES.— List.— Comments  on  it 14-19 

CHAPTER  IV. 

NAMES  AND  SYMBOLS  OF  ELEMENTS.— A  Few  Principles  of  Chemical  Lan- 
guage. —Names  of  Elements.— Symbols  for  Atoms 20-25 

CHAPTER  V. 
CLASSIFICATION  OF  THE  ELEMENTARY  SUBSTANCES.— Metals  and  uon-Metals. .     26-28 

CHAPTER  VI. 
COMPOUND  SUBSTANCES.— Binary  Compounds.— Ternary  Compounds 29-34 

CHAPTER  VII. 
THE  CONSTRUCTION  OF  SUBSTANCES.— Mass,  Molecule,  Atom 85-40 

CHAPTER  VIII. 

How  CHEMICAL  AFFINITY  WORKS.— Each  Atom  has  its  Peculiar  Affinities.— 
Chemical  Affinity  Acts  Only  Under  Favorable  Conditions.— Each  Atom 
has  certain  General  and  Special  Numerical  Preferences.— Chemical  Changes 
Neither  Create  nor  Destroy  Matter.— Chemical  Changes  Produce  Striking 
Results.— Chemical  Changes  are  often  Attended  by  Displays  of  Force.— 
The  Modern  Atomic  Theory,  that  of  Dalton : 41-53 

CHAPTER  IX. 

HYDROGEN.— Where  Found.— Its  Discovery.— Why  not  Discovered  Earlier.— 
How  Prepared  ;  Four  Methods.— Powers  and  Properties  Manifested  by  it.— 
Its  Uses. 58-67 

CHAPTER  X. 

BALLOONS.— Their  Invention.— The  First  Ascension.— Recent  Use  of  Bal- 
loons.—The  Centenary  of  Ballooning 68-78 

CHAPTER  XI. 

CHLORINE.— Its  Distribution.— Its  Discovery.— Its  Preparation.— Its  Character- 
istics.—Hydrochloric  Acid.— Bleaching-Powder 79-92 

CHAPTER  XII. 
BROMINE.— Its   Discovery.— Its   Preparation.— Its   Chemical   Properties.— Its 

Uses 93~97 

CHAPTER  XIII. 

IODINE.— Its  Distribution.— The  Old  Soda  Industry.— The  Leblanc  Process.— 

Discovery  of  Iodine.— Chemical  Properties  of  Iodine 98-104 


CONTENTS. 


CHAPTER  XIV.  PAGE. 

FLUORINE.— Its  Recent  Isolation.— Its  Properties.— Hydrofluoric  Acid 105-109 

CHAPTER  XV. 

OXYGEN.— Its  Importance.— Its  Discovery.— Its  Preparation ;  Two  Methods.— 
Its  Properties.— Ozone.— Allotropism.— Water.— Hydrogen  Dioxide.— Nas- 
cent State.— The  Compound  Blowpipe.— The  Calcium  Light.— Oxygen  as 
Related  to  Combustions,  and  to  Animal  Respiration 110-130 

CHAPTER  XVI. 

WATER.— Its  Abundance.— Its  Importance  to  Living  Beings.— Terrestrial  Cir- 
culation of  Water.— Water  in  the  Solid  Form.— Its  Influence  on  Climate.— 
Its  Action  as  a  Working  Contrivance.— Kinds  of  Water 131-143 

CHAPTER  XVII. 

SULPHUR.— Its  Natural  Sources.— Its  Purification.— Its  Compounds:  Sulphu- 
retted Hydrogen,  Sulphur  Dioxide  and  others 144-154 

CHAPTER  XVIII. 
SULPHUR  TRIOXIDE.— Sulphuric  Acid,  its  History,  Uses,  Manufacture 155-160 

CHAPTER  XIX. 
BORON.— Borax  and  its  Manufacture 161-165 

CHAPTER  XX. 

NITROGEN.— Its  Discovery.— Its  Preparation.— Its  Properties.— Compounds  of 
Nitrogen  and  Hydrogen :  Hydrazine,  Ammonia  Gas  and  its  Properties.— 
Compounds  of  Nitrogen  and  Oxygen :  Nitric  Acid 166-176 

CHAPTER  XXI. 

THE  ATMOSPHERE.— Its  Weight.— Its  Composition.— Offices  of  its  Several  Chief 
Constituents.— Air  Not  a  Chemical  Compound.— Fitness  of  the  Air  for  its 
Purposes 177-183 

CHAPTER  XXII. 

EXPLOSIVES.— Gunpowder.—  Fireworks.—  Fulminates.—  Gun-cotton.—  Nitro- 

glycerin.— Dynamite 184-194 

CHAPTER  XXIII. 

PHOSPHORUS.— Its  Sources.— Its   Agricultural   Use.— Its   Preparation.— Its 

Chemical  Properties.— Friction  Matches 195-206 

CHAPTER  XXIV. 

CARBON.— Charcoal.— Animal  Charcoal.— Lamp-black.— Coal.— Graphite.— The 
Diamond.— Inf  usibility  of  Carbon.— Decolorizing  Power  of  Carbon.— Other 
Natural  Forms  of  Carbon.— Carbon  in  Animal  and  Vegetable  Substances. .  207-225 

CHAPTER  XXV. 

COMPOUNDS  OP  CARBON  AND  OXYGEN.— Carbon  Monoxide.— Carbon  Dioxide. 

Effervescing  Beverages 226-231 

CHAPTER  XXVI. 

ORGANIC  CHEMISTRY.— Definition.— Great  Number  of  Organic  Compounds.— 
Organic  Compounds  Classified :  the  Fatty  Series ;  the  Aromatic  Series  : 
Other  Vegetable  Matters ;  Other  Animal  Matters . .  232-243 

CHAPTER  XXVII. 

ILLUMINATING  GAS.— The  Apparatus  Used.— The  Operation  of  it  Chemically 

Considered.— The  Various  Products . 244-250 

CHAPTER  XXVIII. 
SILICON.— Its  Quantity  in  the  Earth.— Silicic  Oxide  251-254 


CHEMISTRY. 


I. 


BRANCHES  OF   NATURAL  SCIENCE. 

[HEMISTRY  is  properly  classified  as  one  of  the  nat- 
ural sciences.  The  reader  will  doubtless  inquire, 
What  are  the  other  sciences,  and  what  relation 
does  chemistry  bear  to  them?  A  suitable  answer 
to  these  questions  will  go  far  toward  affording  a  compre- 
hensive view  of  the  natural  sciences  in  general,  and  also  a 
definition  of  the  one  with  which  this  book  deals. 

The  general  term  "science,"  originally  meaning  knowl- 
edge, at  the  present  day  means  knowledge  that  has  been 
thoroughly  arranged  and  classified. 

In  the  light  of  this  definition  it  is  plain  that  there  are 
many  more  sciences  than  is  ordinarily  supposed;  and  not 
only  so,  but  that  science  in  its  widest  and  most  appropriate 
signification  may  apply  to  existences  that  are  not  material 
as  well  as  to  the  various  forms  of  matter. 

Any  subject,  therefore,  is  raised  to  the  rank  of  a  science 
when  the  knowledge  about  that  subject  is  placed  in  a  prop- 
erly classified  form  —  that  is,  brought  under  scientific  treat- 
ment. 

Scientific  treatment  has  been  defined  as  the  treatment  of  a 
subject  in  accordance  with  certain  thorough  and  rational 
methods,  involving  at  least  the  following  particulars: 

First.  All  possible  facts  relating  to  the  subject  must  be 
observed  with  the  highest  degree  of  exactness. 


CHEMISTRY. 


Second.  The  facts  observed  must  be  recorded  or  described 
with  a  fixed  unambiguous  nomenclature. 

Third.  The  facts  must  be  arranged  in  order,  the  chief 
facts  preceding  those  that  are  properly  subordinate,  the 
arrangement  being  carefully  studied,  and  harmonizing  as  far 
as  possible  with  the  natural  relations  existing  between 
them. 

Fourth.  The  facts  must  be  bound  together,  and  their  asso- 
ciation with  each  other  must  be  displayed  by  a  ration.-d  and 
intelligible  explanation. 

When  viewed  as  here  presented  it  becomes  evident  that 
the  term  science  is  of  very  wide  application,  while  it  is  true 
that  in  ordinary  e very-day  use  of  language  the  highly  gen- 
eral term  science  is  often  applied  to  natural  science;  but 
natural  science  includes  one  group  of  a  wide  series  of  groups 
of  subjects. 

The  term  natural  science,  then,  is  properly  applied  to  the 
knowledge  of  external  and  material  things,  and  even  then  it 
is  properly  subdivided  according  to  the  kingdom  of  nature, 
or  according  to  the  special  portion  of  nature's  great  field 
with  which  for  the  moment  it  deals. 

In  this  way  two  great  departments  of  natural  science  are 
recognized  :  the  one  called  natural  history,  in  which  are 
included  geology,  zoology,  and  botany  ;  the.  other  called 
natural  philosophy,  or  oftener  physical  science,  in  which  are 
placed  mechanics,  physics  proper,  and  chemistry. 

Chemistry  treats  of  matter  in  its  deepest  recesses  and  its 
smallest  subdivisions — that  is,  it  treats  of  the  atoms  of  matter, 
and  the  changes  of  properties  which  even  vast  quantities  of 
matter  undergo  by  reason  of  changes  in  kind,  in  number,  and 
in  relative  position  of  the  atoms  which,  in  obedience  to  chem- 
ical affinity,  are  gathered  together  into  minute  groups  called 
molecules. 

Undoubtedly  the  beginner  will  experience  some  difficulty 
in  thoroughly  grasping  this  definition  of  the  office  of  chem- 
istry, but  if  he  reads  this  chapter  again  after  he  has  read 
several  of  the  succeeding  ones  it  is  likely  that  the  expres- 


BRANCHES   OF  NATURAL  SCIENCE.  9 

sions  here  will  have  a  newer  and  fuller  meaning  because  of 
the  facts  and  explanations  presented  later  on. 

It  is  not  intended  here  to  offer  a  full  outline  even  fo  all 
the  branches  of  natural  science. 

The  objects  and  the  phenomena  of  the  world  about  us  are 
so  varied  and  so  interwoven  aud  interdependent  that  there 
are  subordinate  natural  sciences  not  quite  coming  under 
either  of  the  topics  we  have  laid  out,  or  which  may  be 
closely  related  to  two  or  more  of  them  at  once. 

It  is  believed,  however,  that  the  explanation  here  given 
will  help  to  show  the  reader  the  proper  position  of  chemistry 
in  the  family  of  natural  sciences. 


10  CHEMISTRY. 


II. 

THE   SCOPE   OF    CHEMISTRY. 

I HEMISTRY  treats  of  all  kinds  of  substances.  This 
is  a  very  broad  assertion,  but  it  appears  to  be  true. 
The  solid  rock  matter  of  the  earth  and  the  wealth 
of  living  animal  and  vegetable  substances  upon  it 
undergo  all  their  varied  changes  in  subjection  to  chemical  laws. 
The  same  is  true  of  the  water,  and  of  all  liquid  things  we 
know  ;  and  the  declaration  applies  yet  further  to  the  invisible 
gaseous  mass  which  surrounds  and  envelops  our  terrestrial 
globe.  This  deeper  but  thinner  ocean  which  we  call  the 
atmosphere  is  also  governed  by  chemical  law  in  all  its  varied 
relations  to  the  living  beings  as  well  as  to  the  inanimate  sub- 
stances that  have  their  existence  within  it.  In  thought  we 
may  ascend  above  these  solid,  liquid,  and  gaseous  substances 
connected  with  our  earth.  When  thus  we  reach  out  to  the 
heavenly  bodies  beyond  we  feel  sure  that  these,  possessing 
as  they  may,  solid,  liquid,  or  gaseous  matter,  are  likewise 
controlled  by  chemical  laws,  and  that  in  their  changes  they 
exemplify  with  more  or  less  fullness  distinct  chemical  prin- 
ciples. 

The  Great  Number  of  Different  Substances  in 
the  Earth. 

Here,  then,  it  is  intimated  that  chemistry  relates  to  an 
enormous  number  of  substances.  In  factr  the  various  kinds 
of  matter  already  recognized  as  existing  on  our  earth  are  so 
numerous  that  they  have  never  been  so  much  as  counted, 
much  less  described  in  any  list  or  volume;  nay,  more,  doubt- 
less many  exist  that  civilized  beings  have  never  recognized 
at  all.  This  last  statement  refers  not  merely  to  such  sub- 
stances as  may  be  known  only  to  savages  dwelling  beyond  the 
reach  of  civilization  and  commerce,  nor  yet  to  such  as  may 


THE  SCOPE   OF  CHEMISTRY.  11 

bo  secreted  in  absolutely  uninhabited  portions  of  the  globe, 
nor  even  to  those  that  exist  so  deep  in  the  earth  that  man's 
power  may  never  be  sufficient  to  reach  them  ;  probably  even 
some  of  the  most  humble  and  familiar  natural  things,  such 
as  blades  of  wheat,  petals  of  daisies,  silks  of  corn,  and  the 
like,  contain  small  quantities  of  distinct  and  separate  com- 
pounds that  have  not  yet  been  recognized  as  such  by  even 
the  most  skillful  chemists. 

But  beyond  all  the  compounds  that  exist  in  the  earth,  rec- 
ognized or  for  various  reasons  unrecognized,  the  chemical 
laws  now  known  suggest  the  possibility  of  producing  arti- 
ficially a  great  multitude  of  additional  substances,  and  even 
more  than  have  yet  been  produced  in  the  great  laboratory 
of  nature. 

How  it  Happens  that  there  is  such  a  Variety. 

By  searching  aright  for  the  secret  of  the  countless  number 
and  the  rich  and  splendid  variety  of  beings  that  nature  and 
art  present  to  the  curious  gaze  of  man,  a  comprehensive 
answer  is  at  last  obtained. 

Forms  of  ordinary  matter  may  be  compared  to  great 
cathedrals,  like  those  of  Cologne  and  of  Milan,  which  have 
been  growing  for  centuries,  and  which,  by  the  combined 
labor  of  artists  and  artisans,  have  at  length  become  intricate 
and  beautiful  structures,  the  admiration  and  delight  of  the 
beholder.  Just  as  these  arise  from  the  combination  in  a 
multitude  of  ways  of  a  comparatively  small  number  of  orig- 
inal and  fundamental  substances — like  stone,  brick,  iron, 
copper,  plaster,  glass,  wood — so  all  things  known  to  chemists 
are  made  up  of  a  few  simple  substances,  either  existing 
alone  or  in  richly  various  combination. 

The  simplest  substances  when  alone  are  called  the  chemical 
dements,  or  elementary  substances;  the  things  resulting  when 
different  elements  are  united  together  are  called  compounds. 
Thus  metallic  iron  is  one  familiar  example  of  a  chemical 
eleme'nt ;  the  oxygen  gas  of  the  atmosphere  is  another 
example,  A  piece  of  iron  exposed  to  damp  air  soon  becomes 


12  CHEMISTRY. 


changed  to  a  mass  of  iron  rust.  This  rust  is  a  compound; 
it  is  made  up  of  iron  and  oxygen  united  together. 

In  the  light  of  what  has  been  said  the  chemical  elements 
assume  a  new  and  grand  importance:  they  are  the  individ- 
uals chosen  by  the  Creator  to  be  the  foundation  stones  and 
the  essential  constituents  of  the  glorious  natural  edifices  of 
his  handiwork. 

Again  when  the  elementary  individuals  unite  they  do  so  by 
reason  of  the  interaction  of  many  and  complex  forces  which 
reside,  almost  like  soul  and  spirit,  within  the  elements. 

These  last  remarks  suggest  the  twofold  character  of 
chemical  study.  It  involves,  First,  the  examination  of  ele- 
mentary substances  and  their  compounds.  Secondly,  it 
requires  a  consideration  of  the  many  general  and  special 
laws  and  forces  which  determine  the  various  possible  com- 
binations. 


READING  REFERENCES. 

In  general,  the  first-mentioned  books  in  each  group  are 
those  which  are  most  accessible  and  at  the  same  time  most 
serviceable.  Some  rare  and  costly  books  are  mentioned,  for 
the  benefit  of  persons  who  have  access  to  large  libraries. 

Chemistry,  General  and  Applied,  Serial  Publications. 

Chemical  News.  (William  Crookes,  Ed.)  London.  "Weekly.  (Com- 
menced 1860.) 

Popular  Science  News  and  Boston  Journal  of  Chemistry.  Boston- 
Monthly.  (Commenced  1867.) 

Journal  of  Chemical  Society.     London.     Monthly. 

Index  to  foregoing.     1841-1872;  pp.  263. 

Annales  de  Chimie  et  de  Physique.     Paris.     Monthly. 

Table  des  Tomes  I  a  XXX.     (1841-1851.)     Paris,     pp.134. 

Table  Analytique  des  Tomes  XXXI  a  LXIX.  3d  Series.  (1851- 

1863.)  Paris,  pp.  474. 

Table  des  Noras  d'Auteurs  et  Table  Analytique  des  Matieres. 

(1864-1873.)  4th  Series.  Paris,  pp.  249. 

Berichte  der  Deutschen  Chemischen  Gesellschaft.  Berlin.  (Com- 
menced 1868.)  20  parts  per  year. 


THE  SCOPE   OF  CHEMISTRY.  13 

Wagner,  Johannes  K.  v. — Jahres-Bericht  iiber  die  Fortschritte  und 
Leistungen  der  chemischen  .Technologic.  Leipzig.  Annual.  (Com- 
menced 1855  ;  last  vol.  had  1,211  pp.) 

Index  to  foregoing.     Vols.  I-X. 

Index  to  foregoing.     Vols.  X-XX. 

Dictionaries  of  Chemistry,  etc. 

Watts,  Henry. — Dictionary  of  Chemistry  and  the  allied  branches  of 

other  sciences.     8  vols.     London.     1865-1875. 
Storer,  Frank  H. — First    Outlines   of   a  Dictionary  of  Solubilities  of 

Chemical  Substances.     Cambridge.     1864. 
Wurtz,  Ad. — Dictionnaire  de  Chimie,  pure  et  appliquee.  3  vols.    Paris. 

1870. 
Fehling,    Hermann   v. — Neues    Handworterbuch  der  Chemie.     A  to 

Phosphorsaure.     Braunschweig.     1871 — now  issuing. 

General  Treatises  on  Chemistry. 

Roscoe,  H.  E.,  and  Schorlemmer,  C. — A  Treatise  on  Chemistry.  Lon- 
don and  New  York.  1878.  Vol.1,  pp.  771;  Vol.  II,  part  I,  pp. 
504,  part  II.  pp.  552;  Vol.  Ill,  part  I,  pp.  724;  parts  II  and  III  also 
issued. 

Cooke,  Josiah  P.,  Jr. — Principles  of  Chemical  Philosophy.     Boston. 

Gmelin,  Leopold  (Henry  Watts,  Tr.) — Hand-Book  of  Chemistry. 
Printed  for  the  Cavendish  Society.  14  vols.  London.  1848-1860. 

Graham-Otto's  Ausfiihrliches  Lehrbuch  der  Chemie.  6  vols.  Braun- 
schweig. 1857. 

Schiitzenberger,  P. — Traite  de  Chimie  ge'nerale.     5  vols.   Paris.    1887. 


U  CHEMISTRY. 


III. 

THE   ELEMENTARY   SUBSTANCES. 

IN  the  following  page  is  a  list  of  the  elementary  sub- 
stances now  generally  recognized  as  such.  Their 
respective  symbols  and  their  atomic  weights,  both 
in  exact  and  approximate  numbers,  are  also  given. 
These  substances,  then,  about  seventy  in  number,  are  those 
from  which  are  made  up  all  material  things  now  known  to 
man.  While  it  is  not  necessary  for  any  one  to  retain  such  a 
list  in  memory,  every  person  who  desires  any  considerable 
knowledge  of  chemistry  should  be  acquainted  with  each  name 
and  the  symbol  attached  to  it,  and  should  know  something  of 
the  natural  sources  and  the  properties  of  the  substances  desig- 
nated. 

Six  Suggestions  Conveyed  by  this  Table. 

A  careful  and  intelligent  reading  of  the  list  affords  several 
important  suggestions.  The  following  are  some  of  them  : 

First.  The  elements  are  not  very  numerous.  They  are  in 
fact  very  few,  as  compared  with  the  countless  number  of  sub- 
stances they  may  form  by  their  proper  combinations. 

Second.  They  are,  however,  sufficiently  numerous  to  pro- 
duce the  many  substances  recognized  in  nature.  For,  consider 
how  human  language  may  have  many  words  and  yet  all 
these  may  be  spelled  out  by  combinations  of  few  letters. 
Some  English  dictionaries  register  over  a  hundred  thousand 
words,  yet  these  are  all  made  by  the  combinations  of  less 
than  thirty  letters.  Now  it  is  easy  to  comprehend  how  the 
few  letters  of  an  alphabet  may  be  even  still  further  combined 
in  various  ways  so  as  to  produce  additional  words  almost  with- 
out limit ;  in  a  similar  manner  it  may  be  easily  imagined  that 
the  elementary  substances  of  the  chemist  have  ample  capabili- 
ties for  giving  rise  not  only  to  the  compounds  now  known,  but 
W  /et  more  and  more,  almost  without  limit.  It  is  true  that 


THE  ELEMENTARY  SUBSTANCES. 


15 


The  Chemist's  Elementary  Substances. 


Name  of 
Element. 

Atomic  Symbol. 

Exact 
Atomic 
Weight. 

Approximate 
Atomic  W'ght. 

Name  of 
Element. 

Atomic  Symbol. 

Exact 
Atomic 
Weight. 

Approximate 
Atomic  W'ght. 

Aluminium.. 
Antimony... 

Al  
Sb  (Stibium)  
As  

27.0090 
119.9550 
74.9180 
136.7630 
2075230 
10.9410 
79.7680 
111.8350 
132.5830 
39.9900 
11.9736 
140.4240 
35.3700 
52.0090 
53.8S70 
63.1730 
144.5730 
165.8910 
18.9810 
63.8540 

9.0850 
196.1550 
1.0000 
113.3980 
126.5570 
192.6510 
55.9130 
138.5260 
206.4710 
7.0073 
23.9590 
55.9060 
199.7120 

27. 
120. 
74.9 
136.8 
207.5 
1(1.9 
79.8 
111.8 
132.6 
40. 
12 
140.4 
35.4 
52. 
58.9 
63.2 
144.6 
165.9 
19. 
68.9 
72.3 
9.1 
196.2 
1. 
113.4 
126.6 
192.7 
55.9 
138.5 
206.5 
7. 
24. 
53.9 
199.7 

Molybdenu.n 
Nickel 

Mo  
Ni    

95.5270 
57.9280 
93.8120 
14.0210 
198.4910 
15.96)3 
105.7370 
30.9580 
19  J.  4150 
39.0190 
101.0550 
85.2510 
104.2170 
150.0210 
43.9800 
78.7970 
28.1950 
107.6750 
22.9980 
87.3740 
31.9840 
182.1440 
127.9600 
203.7150 
233.4140 
117.6980 
47.9997 
183.6100 
238.4820 
51.2560 
172.7610 
89.8160 
64.9045 
89.3670 

95.5 

57.9 
93.8 
14. 
198.5 
16. 
105.7 
31. 
194.4 
39. 
104.1 
85.3 
104.2 
150. 
44. 
78.8 
28.2 
107.7 
23. 
87.4 
32. 
182.1 
128. 
203.7 
233.4 
117.7 
48. 
183.6 
238,5 
61.3- 
172.8 
8.98 
64.9 
89.4 

Niobium  
Nitrogen  — 

Nb  
N  

09 

Barium  

Ba  
Bi  

B  

0  

Br  .  .  .  

Palladium... 
Phosphorus  . 

Pd  

Cadmium  .  .  . 
Caesium  
Calcium  
Carbon 

Cd  
Cs  
Ca  .  

c 

p           

Pt 

Potassium... 
Rhodium  — 
Rubidium 

K(Kalium)  
Rh  
Rb  

Cerium  
Chlorine  
Chromium... 
Cobalt  
Copper  
Didymium.  .  . 

Ce  
CI 

Ruthenium.. 

Ru  
Sm     . 

Cr  
Co  
Cu  (Cuprum)  
D  

Scandium.... 
Selenium  — 
Silicon  

Sc 

ge        

Si  

E.... 

Silver  
Sodium  
Strontium  .  .  . 
Sulphur  
Tantalum  
Tellurium.... 

Ag(Argentum).. 
Na  (Natrium.... 
Sr  
g  
Ta  
Te  
Tl       

p  

Gallium  
Germanium. 
Glucinum  .  .  . 
Gold  

Ga  
Ge  
GorBe(Deryllium 
Au  (Aurum)  
H  

In 

Thorium  
Tin 

Th  
Sn  (Stannum)... 
Ti   

Iridium  .  . 

Titanium  
Tungsten  — 

Iron  
Lanthanum  . 
Lead  
Lithium  
Magnesium.. 
Manganese.. 
Mercury  

Fe  (Ferrum)  
La  
?b  (Plumbum)  .  . 
Li  
Mg  ''  
Mn  

W(Wolframium) 

u  

Vanadium  .. 
Ytterbium... 
Yttrium 

Va  .. 

Yh     

Y  

Zinc  .... 

Zn   

Hg  (Hydrargyrum 

Zirconium... 

Zr  

16  CHEMISTRY. 


the  chemist  discovers  in  some  of  the  chemical  elements  a  limit 
to  the  power  of  union,  but  in  others  he  finds  an  apparently  un- 
bounded capacity  to  form  new  arrangements  and  combinations. 

Third.  Most  of  the  elements  are  uncommon.  Only  about 
one  sixth  of  them  are  familiar  to  ordinary  readers.  Thus 
carbon,  copper,  gold,  iron,  lead,  mercury,  nickel,  silver,  sul- 
phur, tin,  zinc,  are  almost  the  only  names  in  the  list  that  can 
be  said  to  suggest  familiar  things.  Indeed  some  members 
of  this  list  exist  in  the  earth  in  extremely  small  quantities  ; 
but  man  by  his  ingenuity  and  industry  has  gathered  up  even 
these  and  brought  them  near  to  the  hand  of  every  civilized 
being.  Thus  gold  exists  in  the  earth — so  far  as  man  has 
access  to  the  earth — in  only  very  minute  amounts ;  yet  gold 
has  a  multitude  of  common  uses  beside  its  employment  in 
coinage.  Various  forms  of  decorative  art,  like  gilded  letter- 
ing on  books,  afford  familiar  examples.  So  also  mercury, 
which  in  the  ordinary  thermometer  is  very  familiar 
to  every  one,  exists  in  the  earth  in  but  minute  amounts. 

When  the  chemist  examines  still  more  narrowly  the  com- 
position of  the  terrestrial  globe,  he  discovers  an  inequality 
yet  more  extraordinary  than  that  hinted  at.  Thus  it  appears 
that  probably  one  half  of  our  entire  planet  consists  of  a 
single  substance  (that  is,  oxygen)  and  that  one  quarter  of  it 
consists  of  another  single  substance  (that  is,  silicon).  Since 
an  amount  equal  to  three  quarters  of  the  earth's  mat- 
ter, by  weight,  is  made  up  of  but  two  elements,  the  remain- 
ing ones  may  be  expected  to  exist  in  much  smaller  proportions. 

The  following  table,  given  by  Roscoe  and  Schorlemmer, 
shows  the  average  composition  of  the  earth's  crust — so  far  as  it 
is  accessible  to  human  investigation  by  means  at  present  known: 

Percentage  Composition  of  the  Earth's  Solid  Crust. 

(BY  WEIGHT.) 


Oxygen 44.0  to  48.7  per  cent. 

Silicon 22.8       36.2         " 

Aluminium...     9.9         6.1         " 

Iron 9.9         2.4         " 

Calcium 6.6         0.9         u 


Magnesium....     2.7  to   0.1  percent. 

Sodium 2.4         2.5         " 

Potassium..          1.7         3.1         " 


100.0     100.0 


THE  ELEMENTARY  SUBSTANCES.  17 

In  this  table  about  sixty  elements  are  not  mentioned. 
Many  of  these  occur  in  exceedingly  small  quantities  and  also 
in  special  localities.  Their  relative  rarity  is  rendered  all  the 
more  striking  when  it  is  considered  that  in  a  minute  frac- 
tional part  of  the  whole  must  be  included  all  coal  and  all  the 
useful  metals,  except  iron. 

Another  authority  *  declares  that  it  is  probable  that  an 
amount  equal  to  ninety-nine  one  hundredths  of  the  entire 
weight  of  the  solid,  liquid,  and  gaseous  matter  of  our  globe 
is  made  up  of  only  thirteen  elementary  substances.  The 
elements  referred  to  and  their  relative  proportions  are 
approximately  represented  in  the  diagram  following  : 

Diagram  of  the  Composition  of  Our  Globe. 

(BY  WEIGHT.) 


Sulphur,  Hydrogen, 
Chlorine,  Nitrogen, 


About  55 
others. 


Potassium,         Sodium, 
Iron,  Carbon. 

SILICON", 


Aluminium,  1 
Magnesium,  > 
Calcium,  ) 


OXYGEN", 


Fourth.  Most  of  the  elements  are  metals.  This  may  not 
appear  to  the  ordinary  reader  until  he  is  informed  that  ter- 
minations in  um,  as  in  case  of  aluminium,  barium,  cadmium, 
calcium,  and  others,  are  intended  to  suggest  that  the  sub- 


'  Professor  J.  P.  Cooke. 


18  CHEMISTRY. 


stances  so  designated  are  metals.  Most  of  the  other  elements 
having  names  not  terminating  in  um  are  called  non-metals. 

Fifth.  Each  chemical  element  has  an  atomic  symbol,  an 
abridgement,  in  some  form,  of  its  name. 

Sixth.  Each  chemical  element  has  an  atomic  weight.  As 
the  atomic  weight  of  hydrogen  is  1,  without  any  fraction,  it 
is  easily  understood  that  the  weight  of  one  atom  of  hydrogen 
is  taken  as  the  unit  of  the  system.  An  inspection  of  the 
numbers  given  shows  that  in  many  cases  the  atoms  weigh 
amounts  that  are  very  nearly  exact  multiples  of  the  weight 
of  an  atom  of  hydrogen. 


READING  REFERENCES. 
Atomic  Weights,  Calculations  of 

Becker,  George  F. — Atomic  "Weight  Determinations  :  a  digest  of  the 
investigations  published  since  1814.  (Published  as  Part  IV.  of  the 
Constants  of  Nature,  in  Smithsonian  Miscellaneous  Collections,  No. 
358).  1880. 

Clarke,  Frank  W. — A  Recalculation  of  the  Atomic  Weights.  (Published 
as  Part  V.  of  the  Constants  of  Nature,  in  Smithsonian  Miscellaneous 
Collections,  No.  441).  1882. 

• Am.  Chem.  Jour,  iii,  263.     (1881.) 

Atomic  Weights,  Periodicity  of 

Meyer,  Lothar.— Chem.  News,     xli,  203. 

Atomic  Weights,  Mendelejeff  s  Law  of 

Am.  Chem.  Jour. — iii,  455. 

Cooke,  J.  P. — Chem.  Philosophy,     p.  265. 

Wurtz,  Ad.— Atomic  Theory,     p.  154. 

Atomic  Weights,  Arithmetical  Relations  of 

Hodges,  M.  D.  C. — Silliman's  Journal,  3d  Ser.  x,  2ft. 
Nevvlands,  J.  A.  R.— Chem.  News,     xlix,  198. 

Atomic  Weight  of  Oxygen. 

Odling,  W. — Jour,  of  Chem.  Soc.  of  London,     xi,  107. 

Atomic  Weight  of  Thallium. 

Crookes,  Wm.— Chem.  News,  xxix,  14,  29,  39,  55,  65,  75,  85,  97,  105, 
115,  126,  137,  147,  157, 


THE  ELEMENTARY  SUBSTANCES.  19 


Atomic  Weights,  Prout's  Hypothesis  of 

Cooke,  J.  P.— Chemical  Philosophy,  270. 

Clarke,  F.  W.— Arn.  Cliem.  Journal,  iii,  272.     (1881.) 

Gerber, — Silliman's  Journal,  3d  Ser.  xxvi.  236. 

Atoms,  Absolute  Weight  of 

Annaheim,  J. — Jour,  of  Chem.  Soc.  of  London,  xxxi,  31. 

Elements,  Defunct 

Bolton,  H.  C. — American  Chemist,  i,  1. 

Elements,  Suggestions  that  they  are  Compound. 

Lockyer,  J.  X. — Nature,  Jan.  2  and  9,  also  Nov.  6,  1879. 
Hastings,  C.  S. — Criticism  of  above.     Am.  Chem.  Jour.,  i,  15. 
Gladstone,  J.  H.— Chem.  News,  48,  151. 
Brodie,  Sir  B.— Chem.  News,  15,  295. 
Carnelley,  T.— Chem.  News,  53,  183,  197. 
Ciookes,  W. — Chem.  News,  54,  115. 


20  CHEMISTRY. 


IV. 

NAMES  AND  SYMBOLS  OF  ELEMENTS. 

INY  history  of  the  chemical  elements  distinctly  points 
to  the  enormous  stride  which  chemical  discovery 
has  taken  within  the  last  hundred  years.  The 
dawn  of  this  period  was  marked  by  many  most 
important  results.  Among  these  may  be  mentioned  the 
detection  of  the  elementary  gases :  oxygen,  hydrogen,  and 
nitrogen.  The  light  which  these  great  events  threw  upon 
the  future  of  the  science  enabled  the  chemists  of  that  early 
period  to  perceive  that  the  number  of  new  compound  sub- 
stances then  discovered,  and  likely  soon  to  be  discovered, 
called  for  a  multitude  of  new  terms.  In  3787  the  eminent 
French  chemist,  Lavoisier,  in  committee  with  Guyton  de 
Morveau  and  others  of  their  chemical  associates  of  the 
French  Academy,  suggested  a  system  by  which  a  consider- 
able number  of  chemical  compounds,  both  then  known  and 
thereafter  to  be  discovered,  might  be  provided  with  names 
at  once  convenient  and  suggestive.  This  system,  slightly 
modified  and  considerably  extended — to  accommodate  the 
yet  more  widely  expanding  needs  of  the  science — affords  the 
basis  of  the  chemical  language  of  to-day. 

A  Few  Principles  of  Chemical  Language. 

It  is  proposed  to  explain  here  a  few  of  the  first  principles 
of  chemical  nomenclature  and  notation — that  is,  to  present 
a  few  of  the  rules  by  which  significant  and  useful  names  and 
symbols  are  provided.  These  will  be  found  to  supply  the 
requirements  of  hitherto  inaccurately  known  substances,  and 
even  of  those  formerly  unknown. 

Mrst,  the  names  of  elementary  substances  long  known  are 
retained.  Thus,  gold  and  silver  are  metals  that  were 
known  in  the  earliest  historical  periods,  if  not  in  prehistoric 
times  ;  their  names,  therefore,  still  remain  in  use. 


NAMES  AND  SYMBOLS   OF  ELEMENTS. 


Second,  t/ie  discoverers  of  new  elementary  substances  assign 
the  names.  In  so  doing  they  usually  invent  a  name  that  sug- 
gests some  fact  connected  with  the  substance  itself.  Thus 
the  name  nitrogen  is  derived  from  two  Greek  words  (virpov, 
nitron,  mineral  alkali,  and  yzvvcu,),  gennao,  I  produce)  carry- 
ing the  suggestion  that  the  gas  is  one  of  the  constituents  of 
nitre.  The  name  hydrogen  is  derived  from  two  Greek 
words  (vdi^o,  hydor,  water,  and  yevvdu,  f/ennao,  I  produce,) 
indicating  that  wherever  water  exists  hydrogen  is  an  essen- 
tial constituent  of  it.  So  the  name  chlorine  is  derived  from 
a  Greek  word  (%/twpof,  chloros,  green,)  which  reminds  the 
chemist  of  the  fact  that  chlorine  gas  possesses  a  greenish 
color.  The  substance  oxygen,  however,  was  named  in  a 
different  manner.  Its  name  is  derived  from  two  Greek 
words  (o^vg,  oxys,  acid,  and  yevvdb),  gennao,  I  produce,)  sig- 
nifying a  generator  of  acids.  It  appears,  then,  that  in  this 
case  the  name  is  based,  not  on  an  easily  verified  fact,  but 
upon  a  theory,  current  when  oxygen  was  discovered,  of  the 
action  of  the  substance  in  question.  In  a  certain  sense  a  name 
thus  formed  may  be  considered  ill-advised.  Thus  in  the  case 
in  hand  it  has  turned  out  that  while  oxygen  is  a  constituent 
of  a  majority  of  known  acids,  it  is  not  essentially  an  acidifying 
substance  :  many  acids  are  known  that  contain  no  oxygen 
at  all,  and  again  there  are  a  multitude  of  compounds  contain- 
ing oxygen  that  are  not  acids  in  any  proper  sense. 

Third,  newly  discovered  metals  are  usually  given  names 
which,  while  they  suggest  some  property  of  the  substance,  have 
in  addition  the  termination,  um.  Thus  the  metal  thallium 
derives  its  name  from  a  Greek  word  (0aA/lo£,  tliallos,  a  green 
twig,)  which  carries  the  suggestion  of  the  fact  that  thallium 
and  its  compounds  when  highly  heated  evolve  light  of  a 
delicate  green  color.  Again,  caesium,  a  newly  discovered 
metal,  has  a  name  derived  from  a  Latin  word  (caesius,  blue,) 
which  refers  to  the  fact  that  caesium  and  its  compounds 
when  highly  heated  afford  light  of  a  blue  color.  The  ter- 
mination um  is  used  for  metals,  after  the  analogy  of  the 
Latin  language  which  usually  has  its  names  of  metals  end  in 


Fia.  1.— Antoine  Laurent  Lavoisier.    Born  in  Paris,  August  26,  1743;  died  on  tte  scaffold 

in  Paris,  May  8,  1794. 

(22) 


NAMES  AND  SYMBOLS   Off  ELEMENTS.  23 

um.  Indeed,  the  chemist  often  makes  use  of  the  Latin 
names  of  even  those  metals  that  have  been  long  known  by 
more  familiar  ones.  Thus  for  gold  the  Latin  word  aunim  is 
used,  for  silver  the  Latin  word  argentum,  for  lead  the  Latin 
word  plumbum.  It  will  be  seen  later  that  slightly  modified 
forms  of  these  names  are  very  frequently  employed  when 
compounds  of  these  metals  are  to  be  designated. 


Symbols  Used  for  Atoms. 

Each  elementary  substance,  or,  strictly  speaking,  the  mi- 
nute quantity  of  it  represented  by  the  term  one  atom,  may  be 
designated  in  brief  by  a  special  letter  or  short  group  of  letters 
called  the  symbol.  The  usual  symbol  is  the  initial  letter  of 
the  native  or  the  Latin  name  of  the  substance.  Upon  exam- 
ining the  list  of  elementary  substances  at  page  15,  it  will  be 
seen  that  the  following  nine  of  the  names  begin  with  the 
letter  c;  of  course,  therefore,  in  eight  cases  at  least,  the 
symbol  must  contain  an  additional  distinguishing  letter. 


Accordingly  C  indicates  one  atom 
Ca 
Cd 
Ce 
Cl 

Co  " 

Cr  « 

Cs 
Cu  " 


of  Carbon  ; 
Calcium  ; 
Cadmium ; 
Cerium ; 
Chlorine ; 
Cobalt; 
Chromium ; 
Caesium ; 
Copper  (Latin  word  cuprum). 


It  also  appears  that  in  the  case  of  metals,  like  iron  and 
copper,  known  to  the  ancients,  the  symbols  used  are  derived 
from  the  Latin  names.  The  use  of  these  symbols  made  from 
letters — and  therefore  called  literal  symbols,  from  the  Latin 
word  litera,  a  letter — will  become  apparent  as  the  reader 
advances  ;  but  it  is  easily  perceived  that  they  afford  a  con- 
venient abridgment  of  the  longer  titles  of  the  elements. 

The  use  of  literal  symbols  as  an  abridgment  of  the  chem- 
ical nomenclature  was  first  proposed  by  Berzelius,  a  Swedish 
chemist,  whose  eminence  in  every  branch  of  the  science  was 


FIG.  2.— Jons  Jakob  Berzelius. 


Born  in  East  Gothland  (in  Sweden),  August  20,  1799 ;  died 
August  7,  1848. 


NAMES  AND   SYMBOLS    OF  ELEMENTS.  25 

such  that  the  suggestion  here  referred  to  constitutes  one  of 
the  least  of  the  many  and  substantial  grounds  on  which  his 
fame  rests. 


READING  REFERENCES. 
Alchemy. 

Rod  well,  G.  F. — The  Birth  of  Chemistry.     London.     1874. 
Draper,  J.  C. — Amer.  Chemist,  v,  1. 

•    Mackay,  Charles. — Memoirs  of  Extraordinary  Popular  Delusions.     2  v. 
London.     1869.     i,  93. 

Derzelius. 

Wohler,  F. — Early  Recollections  of  Berzelius.     Am.  Chemist,    vi,  131. 

Chemistry,  History  of 

Thomson,  Thomas. — History  of  Chemistry,  2  v.     London.     1830. 
Hoefer,  F. — Histoire  de  la  Physique  et  de  la  Chimfe.     Paris.     1872. 
Kopp,  Hermann. — Gesehichte  der  Chemie.    4Th.  Braunschweig.   1843. 
Die  Entwickelung  der  Chemie  in   der   neueren    Zeit.     Miinchen. 

1873. 

— Die  Alchemie.     2Th.     Heidelberg.     188G. 
Bolton,  H.  C.— Chem.  News,     xxxii,  36,  56,  68. 
Liebig,  J.  v. — Familiar  Letters  on  Chemistry. 
Whewell,  Wm. — History  of  the  Inductive  Sciences.     2  v.     New  York. 

1875.     ii,  259. 

Lavoisier. 

Thomson,   Thomas.— History   of    Chemistry.     2   v.      London.     1830. 

ii,  75. 

Figuier  L. — Vies  des  Savants  Tllustres  du  xviii  siecle,  444. 
Brougham,    H.— Lives    of    Philosophers  of    the  time  of  George   III. 

Edinburgh.     1872.     290. 
Grimaux,    E. — La   mort  de  Lavoisier.      Revue    des    Deux    Mondes. 

LXXIX.     884. 

nomenclature. 

Morveau,  Guyton  de. — Mcmoire  sur  les  denominations  chimiques,  la 
necessite  d'en  perfectionner  le  systeme,  les  regies  pour  y  parvenir, 
suivi  d'un  tableau  d'une  nomenclature  chemique  ;  Dijon.  1782. 

Lavoisier,  de  Morveau,  Fourcroy.  Baume,  Hassenfratz,  Adet  and  others. 
Methode  de  nomenclature  chimique.  Paris.  1787.  (The  Boston 
Athenaeum  Library  contains  a  copy  of  this  work.) 

Gmelin's  Proposed  Nomenclature. 

Wurtz  Dictionnaire.     ii.     Part  I.     575. 
Gmelin  Hand-Buch.     v,  132. 

Odling,  W.— Chem.  News,  52,  181,  203,  216.  (Plea  for  the  empiric 
naming  of  compounds.) 


26  CHEMISTRY. 


V; 

CLASSIFICATION  OF  THE  ELEMENTARY 
SUBSTANCES. 

speaking  of  the  elementary  substances  some  of 
them  have  been  referred  to  as  metals.  What,  then, 
is  the  exact  idea  conveyed  by  this  designating 
term  ?  Every  one  can  readily  picture  in  his  mind 
some  metal  or  metals  like  gold,  silver,  tin,  zinc,  and  others,  that 
have  certain  common  characteristics,  such  as  great  weight,  and 
the  peculiar  brilliancy  and  power  of  reflecting  light  which  is 
described  as  metallic  lustre.  Another  well  marked  and 
widely  recognized  characteristic  at  once  thought  of  is  the 
facility  with  which  the  substances  ordinarily  known  as  metals 
may  be  beaten  or  rolled  into  thin  layers.  This  property, 
called  malleability  (a  word  derived  from  the  Latin  word 
malleus,  a  hammer),  is  not  possessed  in  any  striking  degree 
by  substances  other  than  metals.  Thus,  sulphur  is  not  malle- 
able— quite  the  contrary;  it  is  very  brittle.  Charcoal,  which 
consists  mostly  of  the  elementary  substance  called  carbon,  is 
likewise  not  malleable  ;  neither  of  these  last  two  substances 
would  be  likely  to  be  considered  by  even  an  ordinary 
observer  as  metals.  In  fact  they  are  classed  as  non-metals 
by  the  chemist.  This  division  of  the  elementary  substances 
into  metals  and  non-metals  is  dwelt  upon,  not  because  it  can 
be  called  a  very  important  one,  but  because  it  is  widely  used 
in  works  on  chemistry  and  because  in  deciding  to  which  of 
these  two  classes  a  given  substance  belongs,  ultimate  depend- 
ence must  be  placed  upon  its  chemical  characteristics  rather 
than  upon  its  mere  mechanical  properties. 

The  Meanings  Associated  with  the  Term  Metal. 

The  principal  properties  referred  to  are  best  presented  in 
three  groups  : 

First.  Metallic  Properties    Associated  with    Mechanical 


CLASSIFICATION  OF  THE  ELEMENTS.  27 


Relations. — An  elementary  substance  accepted  as  a  metal 
must  possess  the  property  of  existing  in  a  solid  condition  ;  a 
weight  rather  greater  than  that  of  most  well-known  sub- 
stances ;  considerable  hardness,  malleability,  ductility  (that 
is,  the  capability  of  being  drawn  out  into  fine  wire). 

Second.  Metallic  Properties  Associated  with  Physical  Rela- 
tions.— A  metal  should  possess  the  metallic  lustre;  the  power 
called  opacity,  by  reason  of  which  it  does  not  allow  light  to 
pass  through  it  ;  the  noticeable  capability  of  allowing  heat 
to  flow  in  it,  called  the  power  of  conducting  heat  ;  the  capac- 
ity for  allowing  the  electric  current  to  flow  readily  in  it,  called 
good  conducting  power  for  electricity. 

Third.  Metallic  Properties  Associated  with  Chemical  Rela- 
tions.— A  metal  should  possess  the  power  and  the  tendency 
to  readily  form  a  chemical  union  with  oxygen  ;  the  chemical 
power  to  act  upon  compounds  containing  hydrogen  in  such 
a  way  as  to  turn  the  hydrogen  out  and  take  its  place  in 
the  old  compound  and  thus  form  a  new  one  ;  the  relationship 
toward  the  electric  current  such  that,  when  the  element  is 
subjected  to  the  galvanic  battery,  it  tends  to  gather  about 
the  negative  pole — in  consequence  of  which  characteristic  it 
is  usually  called  electro-positive. 

But  while  no  known  metal  appears  to  possess  the  entire 
range  of  properties  with  which  in  thought  the  ideal  one  is 
endowed,  every  substance  classified  as  a  metal  should  possess 
many  of  them. 

An  illustration  of  what  has  been  said  may  be  found  in 
metallic  mercury.  From  the  fact  that  under  ordinary  con- 
ditions it  is  a  liquid  it  is  plain  that  mercury  must  lack  certain 
of  the  metallic  properties  referred  to;  that  is,  it  does  not 
possess  the  solid  form,  it  does  not  possess  hardness,  it  does 
not  possess  malleability,  it  does  not  possess  ductility.  Yet 
if  it  is  cooled  to  a  low  temperature — about  forty  degrees 
below  zero — it  freezes;  in  other  words,  becomes  solid;  then 
it  possesses  many  of  the  distinctly  metallic  features  that  it 
necessarily  lacks  when  in  the  ordinary  liquid  condition.  Of 
course  this  liquid  condition  is  a  mere  incidental  circum- 


28  CHEMISTRY. 


stance,  due  to  the  temperature  which  ordinarily  prevails  upon 
our  earth.  If  our  ordinary  temperature  were  slightly  lower 
than  forty  degrees  below  zero  mercury  would  then  be  com- 
monly known  as  a  solid,  hard,  lustrous,  heavy,  malleable 
metal — capable,  of  course,  of  melting  with  a  slight  accession 
of  heat. 

As  a  further  illustration,  in  a  somewhat  different  direction, 
mention  may  be  made  of  the  metal  lithium.  This  substance 
cannot  be  called  heavy,  since  it  is  lighter  than  water;  indeed 
it  is  the  lightest  solid  known.  But  on  the  other  hand  it  pos- 
sesses in  a  striking  degree  those  chemical  features  of  metals, 
such  as  strong  affinity  for  oxygen  and  tendency  to  combine 
with  it,  which  have  already  been  detailed  in  our  definition 
of  the  ideal  metal. 

The  Term  Non-Metal. 

The  term  non-metal  is  suggestive  of  a  negative  idea,  and 
not  of  any  definite  or  positive  one.  In  fact  it  is  intended  to 
intimate  that  elementary  substances  of  this  class  are  those 
which  do  not  properly  belong  to  the  other.  Sulphur  and 
carbon  have  been  already  alluded  to  as  examples  of  non- 
metals ;  other  non-metals,  such  as  oxygen,  hydrogen,  nitro- 
gen, fluorine  nnd  chlorine  among  the  gases,  bromine,  a  liquid, 
and  iodine,  antimony,  phosphorus,  arsenic,  boron,  silicon  and 
selenium,  among  solids,  are  far  less  familiarly  known  to  most 
persons. 

READING    REFERENCES. 
Elements,  Classification  of 

Williamson.  A.  W. — Jour,  of  Chem.  Soc.  of  London,     xvii,  211. 
Chemical  Theory. 

Cooke,  Josiali  P.,  Jr.— The-Xew  Chemistry.     New  York.     1874. 

Remsen,    Ira. — Principles   of  Theoretical    Chemistry.       Philadelphia. 
1887. 

Tilden,  William  A. — Introduction  to  the  Stud}' of  Chemical  Philosophy. 

Wurtz,  Ad.     (Henry  Watts,  Tr.)— History  of  Chemical  Theory.     Lon- 
don.    1869. 


COMPOUND   SUBSTANCES.  29 


VI. 

COMPOUND    SUBSTANCES. 

a  previous  chapter  a  list  of  elementary  sub- 
stances has  been  given.  All  other  matters  known 
are  compounds.  From  what  has  been  said  already 
it  is  evident  that  the  compounds  are  very  numer- 
ous, indeed  that  there  is  practically  no  limit  to  the  number 
of  possible  ones.  These  compounds  are  all  made  up  by  the 
union  of  elementary  substances  in  obedience  to  the  peculiar 
chemical  forces  that  reside  within  them.  Some  compounds 
have  only  two  kinds  of  elements:  they  are  called  binaries. 
Some  compounds  have  three  kinds  of  elements:  they  are 
called  ternaries.  Other  compounds  may  have  four,  five,  six, 
or  even  more  kinds  of  elements  grouped  together  to  form 
one  sort  of  substance.  It  this  place  reference  will  be  made 
principally  to  binaries  and  ternaries  —  that  is,  to  the  com- 
pounds of  the  simpler  forms  of  constitution. 

Examples  of  Binary  Compounds. 

In  discussing  binaries  it  will  be  well  to  give  at  the  outset 
three  or  four  examples  for  the  purpose  of  illustration. 

First.  The  gas  known  as  hydrogen  and  the  gas  known  as 
chlorine  have  the  power  of  combining  chemically  and  pro- 
ducing an  entirely  new  compound,  a  compound  different  from 
hydrogen  and  different  from  chlorine,  yet  containing  por- 
tions of  each  of  them.  This  compound  is  a  binary  since  it 
consists  of  but  two  kinds  of  elements.  It  has  several  names, 
one  of  which  is  hydric  chloride.  The  chemist  frequently  repre- 
sents what  is  evidently  the  smallest  possible  quantity  of  this 
substance,  and  also  its  exact  composition,  by  the  expression 

H  01. 

It  is  plain  that  this  expression  means  a  minute  portion  of 
substance  formed  by  the  union  of  one  atom  of  hydrogen, 


30  CHEMISTRY. 


(expressed  by  II,)  and  one  atom  of  chlorine   (expressed  by 
Cl). 

Second.  When  sulphur  burns  in  the  air  it  produces  a  blue 
flame.  At  the  same  time  a  new  and  peculiar  gas  is  formed 
which  is  easily  recognized  by  its  choking  odor,  similar  to 
that  given  off  by  a  burning  sulphur  match.  Now  this  odor 
is  one  of  the  properties  of  a  new  compound  that  has  been 
formed:  a  compound  different  from  sulphur,  different  from 
oxygen,  yet  containing  them  both  and  produced  by  the  union 
of  them.  The  compound  is  a  binary  because  it  contains  but 
two  kinds  of  elements.  It  is  called  sulphur  dioxide.  The 
name  is  intended  to  suggest  that  there  are  two  atoms  of 
oxygen  to  one  of  sulphur  in  the  compound.  This  idea  is 
further  conveyed  by  the  abridged  system  of  notation  so 
commonly  used  by  chemists.  Thus  by  this  system  the 
smallest  possible  quantity  of  the  compound  in  question  is 
expressed  as  follows, 

S02. 

In  this  expression  it  is  very  plain  that  S  stands  for  one  atom 
of  sulphur,  and  O.^  for  two  atoms  of  oxygen. 

Third.  But  sulphur  may  be  made  to  combine  with  a  still 
larger  amount  of  oxygen  than  it  takes  when  it  simply  burns 
in  the  air.  Then  it  forms  a  compound  called  sulphur  triox- 
ide.  This  is  still  a  binary,  since  it  contains  nothing  but  sul- 
phur and  oxygen — that  is,  only  two  elementary  substances. 
Expressed  in  the  briefer  form  the  smallest  quantity  of  this 
compound  may  be  expressed  by  the  formula, 

S03. 

This  expression  means  a  compound  arising  from  the  union  of 
one  atom  of  sulphur  and  three  atoms  of  oxygen. 

Fourth.  When  lead  is  heated  to  the  melting  point  in  the 
dir  it  is  observed  to  become  coated  with  a  constantly  increas- 
ing mass  of  a  kind  of  ashes.  A  pound  of  the  lead  when 
heated  in  this  way  produces  considerably  more  than  a  pound 
of  dross.  The  formation  of  this  dross  is  explained  by  the 
fact  that  when  lead  is  heated  it  really  burns,  though  of 


COMPOUND   SUBSTANCES.  31 

course  the  rapidity  of  the  burning  depends  upon  the 
amounts  of  heat  and  air  to  which  the  lead  is  subjected. 
Evidently  the  lead,  in  burning,  has  something  added  to 
itself.  That  something  is  a  gas  which  is  ever  present  in  the 
atmosphere  and  which  is  called  oxygen.  The  dross  is  a 
chemical  compound  of  lead  and  oxygen.  It  is  called,  plumbic 
oxide,  and  its  smallest  quantity  is  represented  by  the  for- 
mula, 

PbO. 

In  this  formula  it  is  easy  to  see  that  Pb  stands  for  an  atom 
of  lead  (whose  Latin  name  is  plumbum),  and  O  for  an  atom 
of  oxygen.  The  dross,  then,  is  a  binary  compound. 

A  multitude  of  such  examples  of  binary  compounds  might 
be  given ;  probably  those  already  cited  are  sufficient  for  the 
present.  It  will  be  advantageous  to  the  reader  to  carefully 
learn  the  names  and  the  formulas  of  the  binary  compounds 
thus  far  given,  since  they  are  selected  examples  which  may 
be  used  again  further  on. 

Examples  of  Ternary  Compounds. 

The  ternary  compounds  are  those  which  consist  of  three 
kinds  of  elements  ;  of  course  they  are  more  complicated  in 
structure  than  the  binaries.  This  fact,  however,  must  not 
deter  the  reader  from  the  attempt  to  understand  them  at  the 
outset,  for  the  principal  ternaries  are  acids  and  salts,  and 
every  one  knows  that  acids  and  salts  are  among  the  most  im- 
portant compounds  which  the  chemist  has  to  employ. 

As  examples  of  ternary  acids  mention  will  be  made  of 
two  of  the  principal  ones  used  by  the  chemist. 

And  first,  nitric  acid  is  a  compound  of  hydrogen,  nitrogen, 
and  oxygen.  The  formula  of  the  smallest  individual  portion 

of  it  is 

HN03 

These  letters  signify  that  nitric  acid  contains  one  atom  of 
hydrogen,  combined  with  one  atom  of  nitrogen  and  three 
atoms  of  oxygen.  Now  this  nitric  acid  forms  a  great  many 
salts.  A  simple  example  may  be  found  in  that  one  contain- 


32  CHEMISTRY. 


ing  silver.  Thus  when  nitric  acid  and  silver  are  warmed 
together,  either  a  part  or  the  whole  of  the  silver  dissolves. 
A  new  substance  is  produced  which  is  commonly  called 
nitrate  of  silver.  By  the  chemist  it  is  oftener  called  argen- 
tic nitrate.  Its  solution  may  be  dried  into  the  form  of  a 
white  crystalline  substance,  one  that  has  long  been  accepted 
as  a  member  of  the  class  of  salts.  Its  formula  is 

AgN03. 

It  is  plain  that  this  last  formula  is  employed  as  a  short 
way  of  expressing  that  the  salt  is  a  compound  of  more  than 
one  kind  of  element — of  three  kinds  in  fact — and  that  these 
elements  are  in  the  proportions  of  one  atom  of  silver,  one 
atom  of  nitrogen,  and  three  atoms  of  oxygen. 

Promise  was  made  to  refer  to  two  important  acids  ;  sul- 
phuric acid  is  the  second  one.  Commercially  this  substance 
is  by  far  the  most  important  of  all  the  acids.  Indeed,  its 
manufacture  is  one  branch  of  the  greatest  chemical  indus- 
try devised  by  man — the  alkali  trade.  Evidently  it  is  im- 
portant that  the  chemist  should  be  thoroughly  acquainted 
with  sulphuric  acid;  with  its  composition,  its  formula,  its 
way  of  chemically  acting  on  other  substances,  and  the  things 
or  products  that  it  gives  rise  to  when  it  has  opportunity  so 
to  act.  Now  sulphuric  acid  has  the  formula 

H2S04. 

This  formula  means  that  sulphuric  acid  is  a  ternary,  being 
made  up  of  three  different  kinds  of  elements  ;  namely,  two 
atoms  of  hydrogen,  one  atom  of  sulphur,  and  four  atoms  of 
oxygen. 

Further,  sulphuric  acid  forms  a  large  number  of  salts. 
Thus  it  forms  one  containing  silver.  This  is  commonly 
called  sulphate  of  silver,  though  the  chemist  generally  calls 
it  argentic  sulphate.  The  formula  of  argentic  sulphate  is 

Ag2S04. 

When  this  formula  is  firmly  acquired  by  the  reader  so  that 
he  can  readily  compare  it  with  others  already  mentioned,  a 


COMPOUND  SUBSTANCES.  33 


certain  simple  and  distinct  relationship  may  be  traced.  Thus 
comparing 

Argentic  sulphate,  Ag2S04 

with  Sulphuric  acid,  H2S04 

it  is  evident  that  in  the  one  two  atoms  of  silver  have  taken 
the  place  of  two  atoms  of  hydrogen  that  appeared  in  the 
other.  And  such  is  usually  the  case:  when  silver  takes  the 
place  of  hydrogen,  it  does  so  atom  for  atom.  Indeed  argen^ 
tic  nitrate,  AgNO3,  already  described,  illustrates  this  fact. 
It  is  a  compound  product  closely  related  ta  nitric  acid, 
HNO3,  the  only  difference  of  construction  being  that  here 
also  one  atom  of  silver  has  taken  the  place  of  one  atom  of 
hydrogen. 

The  Purpose  of  this  Chapter. 

The  purpose  of  this  chapter  has  been  to  suggest  a  few 
facts  respecting  the  nature  of  chemical  compounds  and  also 
to  show  how  the  science  of  chemistry  employs  its  peculiar 
language  both  in  its  longer  and  shorter  forms.  This  lan- 
guage is  very  comprehensive.  In  fact  it  is  too  elaborate  for 
full  explanation  here.  The  plan  contemplated  is  to  give  at 
this  point  a  few  hints  as  to  its  nature  and  scope,  and  to  de- 
velop it  only  so  far  as  may  be  necessary  to  the  succeeding 
stages  of  our  progress. 

It  is  proper  to  suggest  at  this  point  that  no  single  scientific 
man — nor  society  of  them — can  enforce  the  use  of  any  par- 
ticular words  upon  the  great  body  of  chemists.  For  this 
reason,  as  well  as  for  others,  there  still  prevails  the  use  of 
different  chemical  names  for  the  same  substance.  Thus  the 
compound  of  hydrogen  and  chlorine  first  referred  to  as  rep- 
resented by  the  formula  H  Cl,  has  at  least  four  widely  used 
names:  first,  a  name  merely  suggestive  of  its  component 
parts — that  is,  hydric  chloride  ;  second  and  third,  names 
which  suggest  something  in  addition  to  its  component  parts; 
namely,  that  it  is  an  acid — thus  it  is  called  both  hydro  chloric 
acid  and  chlorohydric  acid ;  fourth,  an  old-fashioned  name 
3 


CHEMISTRY. 


which  still    retains  its    hold    upon    the  commercial   world, 
namely,  muriatic  acid. 

This  same  general  principle  applies  to  a  great  many  other 
substances,  and  while  it  is  true  that  it  thus  increases  the 
number  of  names  in  the  chemical  language,  it  likewise  inci- 
dentally enriches  that  language.  For  in  many  cases  it  has 
come  to  pass,  little  by  little,  that  these  different  names  are 
appropriated  to  slightly  different  forms  of  the  same  sub- 
stance, and  so  the  name  employed  often  conveys  to  the  intel- 
ligent chemist  as  definite  a  shade  of  meaning  as  do  the 
different  synonyms  used  in  the  description  of  every-day 
affairs  by  any  accomplished  author.  A  single  example  will 
elucidate  this  point.  The  term  oil  of  vitriol  would  usually 
be  defined  as  meaning  sulphuric  acid.  But  the  words  sul- 
phuric acid  convey,  strictly  speaking,  the  same  meaning  as 
the  formula 

H2S04 

This  latter  substance,  however,  is  of  very  rare  occurrence 
alone  ;  it  is  flsually  associated  with  varying  quantities  of 
water,  and  is  then  spoken  of  as  sulphuric  acid  of  varying 
degrees  of  dilution.  Now  the  manufacturing  chemists  of 
the  United  States  have  adopted  a  definite  mixture  of  sul- 
phuric acid  (H2SO4)  and  water  (H2O)  as  an  exact  thing  to  be 
called  oil  of  vitriol.  It  is  that  dilution  consisting  of 

93.5  per  cent,  of  sulphuric  acid,  H2S04 

with    6.5  per  cent,  of  water,  H20 

both  taken  by  weight. 


READING    REFERENCES. 
Notation,  Chemical. 

Frankland,  E. — Experimental  Researches  in  Chemistry.     8.     London. 

187Y. 

Williamson,  A.  W. — Jour,  of  Chem.  Soc.  of  London,     xvii,  421. 
Frankland,  E.— Loc.  cit     xix,  372. 
Madan.  H.  G.— Loc.  cit.     xxiii,  22. 

Council  Chem.  Soc.  of  London. — Instruction's  to  Abstractors  from  Cur- 
rent Publications.     (1879.)     Chem.  News,     xlvii,  15. 


THE    CONSTRUCTION  OF  SUBSTANCES. 


VII. 

THE    CONSTRUCTION    OF    SUBSTANCES. 

order  to  understand  the  chemical  construction 
of  substances  it  is  necessary  to  consider  three 
terms  much  used  by  the  chemist;  these  terms 
are  : 

Mass. 

Molecule, 

Atom. 

Evidently  the  words  relate  to  three  grades  of  magnitude 
in  which  matter  is  capable  of  existing  ;  it  is  equally  plain 
that  of  the  series  the  mass  represents  the  largest  individual 
portion  of  substance,  and  the  atom  the  smallest,  while  the 
molecule  represents  the  intermediate  one. 

The  Chemical  Use  of  the  Term  Mass. 

Whoever  looks  about  him  sees  substances  existing  in 
masses.  This  is  true  of  vast  mountain  chains  and  equally  true 
of  the  smallest  grains  of  matter  that  are  recognized  as  the 
humblest  components  of  those  peaks. 

But  the  smallest  of  these  visible  masses  is  made  up  of  par- 
ticles still  more  minute — yet,  perhaps,  of  precisely  the  same 
kind.  For  the  chemist  possesses  means  of  subdivision  of 
substances  by  which  he  may  make  them  into  minute  frac- 
tional parts  that  are  measurable  and  are  all  just  alike,  and 
he  may  continue  this  process  long  after  the  portions  have 
sunk  below  the  reach  and  range  of  ordinary  vision.  A 
lump  of  pure  sugar  as  big  as  a  cubic  inch  may  be  mechanic- 
ally divided  by  any  one  into  many  smaller  ones,  each  little 
one  being  easily  recognized  by  the  ordinary  senses  as  possess- 
ing the  sweetness,  the  crystalline  construction,  the  white- 
ness, the  solidity,  the  brilliancy,  the  power  of  dissolving  in 
water,  and  perhaps  other  well-known  characteristics  that  per- 


36  CHEMISTRY. 


tain  to  sugar.  But  the  chemist  is  able  to  continue  the  sub- 
division of  the  sugar  much  further.  This  he  does  by  recourse 
to  processes  not  exactly  mechanical,  though  closely  allied  to 
them  ;  by  processes  often  called  physical  as  distinguished 
from  purely  mechanical  ones.  He  may  thus  reduce  the 
sugar  to  fragments  of  such  extreme  minuteness  that  while 
they  do  not  impress  our  senses  as  larger  portions  do,  yet  each 
fragment  is  capable  of  displaying  to  a  competent  scientific 
observer  the  certain  and  sure  chemical  properties  that  always 
belong  to  sugar,  whether  in  large  lumps  or  in  small  ones,  and 
which  in  fact  belong  to  nothing  but  sugar. 

Speaking  generally,  all  particles  producible  by  mechanical 
subdivision  are  masses,  while  the  same  is  true  of  most  par- 
ticles producible  by  physical  subdivision. 

The  Chemical  Use  of  the  Term  Molecule. 

But  there  is  a  point  where  any  attempt  at  further  scien- 
tific subdivision  results  in  a  new  and  startling  change  :  at 
this  stage  the  last  individual  that  can  properly  be  called 
sugar  is  dissected  and  loses  entirely  the  characteristics  of 
sugar.  The  fragments  produced  by  the  wreck  of  the  last 
particle  are  of  a  new  kind.  They  are 

portions  of  carbon, 
portions  of  hydrogen, 
portions  of  oxygen. 

This  last  particle  of  sugar  is  separated  into  its  ultimate 
constituents  only  by  chemical  processes.  This  last  particle 
before  it  is  broken  up  is  called  the  molecule,  the  word  mean- 
ing a  little  portion.  The  single  individual  thing  it  refers  to 
cannot  be  detected  by  the  eye,  nor  can  it  be  in  any  way 
appreciated  except  by  scientific  means.  But  a  chemical 
change  of  the  last  multitude  of  molecules  at  once,  is  practica- 
ble to  every  body,  and  it  is  to  a  certain  extent  recognized  by 
every  one  who  heats  sugar  until  it  turns  to  a  charred  mass. 
This  charred  mass  is  mainly  carbon — one  of  the  components 
of  the  now  ruined  sugar — and  it  is  very  unlike  sugar  in  every 


THE   CONSTRUCTION  OF  SUBSTANCES.  37 

way.  The  chemist  can  show  that  when  sugar  is  charred  the 
oxygen  and  the  hydrogen  go  off  mostly  in  the  form  of  gases 
or  vapors,  and  that  on  this  account  they  escape  detection  at 
the  hands  of  all  ordinary  observers. 


The  Chemical  Use  of  the  Term  Atom. 

It  appears,  then,  that  the  chemist  is  able  to  subdivide 
molecules  into  smaller  parts.  But  he  finds  that  in  the  pres- 
ent state  of  our  knowledge  of  matter  further  subdivision  is 
impracticable.  He  can  take  the  oxygen  out  of  the  sugar,  but 
he  cannot  take  anything  but  oxygen  out  of  oxygen;  he  can 
take  hydrogen  out  of  sugar,  but  he  cannot  take  any  thing  but 
hydrogen  out  of  hydrogen  ;  he  can  take  carbon  out  of  sugar, 
but  he  cannot  take  any  thing  but  carbon  out  of  carbon. 

As  a  result  of  all  chemical  study  of  common  sugar  the 
chemist  has  fixed  upon  the  following  as  expressing  most 
closely  the  facts  as  he  knows  them  : 

The  formula 
of  one  molecule  of  pure  cane  sugar  is 


The  chemical  formula  of  any  substance  expresses  much 
more  than  the  reader  would  at  first  imagine.  Thus  the  for- 
mula CigHgsOn  conveys  at  once  to  the  chemist  a  series  of 
facts,  some  of  which  may  be  amplified  as  follows  :  one  mole- 
cule of  sugar  contains  three  kinds  of  substance  :  carbon, 
hydrogen  and  oxygen  ;  each  of  these  kinds  of  matter  exists 
in  the  molecule  in  separate  minute  portions  such  as  in  the 
present  state  of  human  knowledge  are  divisible  only  in  a 
limited  way;  thus  the  carbon  of  one  molecule  of  sugar  is 
divisible  into  twelve  parts,  and  no  further  ; 

the  hydrogen  of  one  molecule  of  sugar  is  divisible 
into  twenty-two  parts,  and  no  further; 

the  oxygen  of  one  molecule  of  sugar  is  divisible 
into  eleven  parts,  and  no  further. 


CHEMISTRY. 


Definition  of  the  Term  Atom. 

Now  at  last  the  atom  has  been  reached.  It  is  that  portion 
of  any  kind  of  matter  that  is  to  human  beings — for  the 
present,  at  least — indivisible  in  fact.  It  has  already  been 
stated  that  there  are  only  about  seventy  different  kinds  of 
atoms;  it  appears,  then,  that  there  are  only  seventy  kinds  of 
matter  that  at  present  cannot  be  chemically  subdivided 
into  different  components. 

It  is  true  that  some  persons  consider  that  certain  intricate 
chemical  processes  suggest  that  what  have  been  here  called 
indivisible  atoms  are  themselves  really  capable  of  yet  further 
decomposition.  Without  attempting  here  to  sustain  or  to 
demolish  this  proposition,  or  to  say  what  the  future  of  chemi- 
cal investigation  may  reveal,  it  may  be  safely  remarked  that 
adequate  proof  has  not  yet  been  offered  of  the  ability  of  any 
one  to  successfully  accomplish  a  decomposition  of  the  atoms 
enumerated.* 

Plainly,  then,  just  as  bricks  may  be  made  into  a  building, 
and  a  series  of  buildings  may  make  a  city,  and  a  series  of 
cities  may  exist  in  a  State,  so  atoms  may  combine  together 
to  form  molecules,  and  molecules  may  cohere  together  to 
form  a  mass,  and  visible  masses  may  be  placed  side  by  side 
and  give  rise  to  the  ordinary  objects  recognized  about  us. 
True,  the  comparison  suggested  is  not  strictly  carried  out  in 
all  particulars.  But  the  difficulty  is  not  a  serious  one  ;  for 
a  city  might  contain  a  multitude  of  houses  each  one  so 
similar  that  no  difference  could  be  distinguished  between 
them,  just  as  a  mass  of  sugar  does  in  fact  contain  molecules 
of  which  each  one  is  so  like  its  neighbor  that  the  most 
refined  chemical  methods  discover  no  difference  between 
them.  Again,  these  same  houses  might  be  composed 
of  combinations  of  brick  and  other  materials  differing 
among  themselves,  but  closely  corresponding  in  every  house. 
So  the  molecule  of  sugar  does  contain  certain  atoms  of  car- 
bon, hydrogen  and  oxygen,  the  atoms  of  one  kind  differ- 

*  See  references  (on  page  19)  to  suggestions  that  our  so-called  elements  are  in  fact 
compound. 


THE   CONSTRUCTION  OF  SUBSTANCES.  39 

ing  distinctly  and  absolutely  from  the  atoms  of  the  other 
kind. 

But  here  the  parallelism  seems  to  cease.  For  while  all 
bricks  and  other  components  of  a  building  are  capable  of 
being  split  into  smaller  portions,  the  atoms  composing  the 
molecule  are  found  by  the  chemist  to  be  absolutely  indivis- 
ible, in  the  present  state  of  knowledge. 

Employing  still  further  the  illustration  already  in  hand  it 
maybe  added  that  just  as  the  walls  of  a  dwelling  might  con- 
tain bricks  either  of  the  same  kind  as  to  their  color,  shape 
and  weight,  or  else  differing  in  these  or  other  respects,  so  a 
molecule  may  be  a  little  group  of  atoms  of  the  same  kind,  or 
it  may  be  a  group  of  atoms  of  different  kinds.  Thus  the 
hydrogen  gas  molecule  is  composed  of  two  atoms  each  just 
alike,  and  each  being  hydrogen.  This  molecule  is  represented 

by  the  formula 

H,  or  H— H. 

So  a  molecule  of  chlorine  gas  is  composed  of  two  atoms 
each  just  alike  and  each  being  chlorine.  This  molecule  is 
represented  by  the  formula 

Cla  or  Cl— Cl. 

Everything  Built  up  of  Atoms. 

Now  each  of  the  elementary  substances  has  molecules 
composed  of  atoms,  and  each  molecule  of  a  given  element  is 
composed  of  atoms  of  the  same  kind.  And  further  all  the 
vast  and  countless  myriad  of  compound  substances,  whether 
buried  in  the  heart  of  the  solid  earth,  whether  drifting  in  the 
wandering  courses  of  the  ocean's  currents,  whether  floating 
in  the  airy  mass  which  is  wrapped  about  our  globe,  whether 
components  of  distant  planets — all  these  substances  are  con- 
structed, so  far  as  we  know,  of  inconceivably  minute  atoms 
of  varying  kinds  bound  together  by  chemical  attraction  into 
molecules,  the  molecules  being  piled  one  upon  another  into 
those  masses  whose  reaction  our  dull  senses  can  appreciate. 
It  may  be  that  our  great  central  luminary,  the  sun,  has  its 
atoms  combined  in  molecules  also.  Perhaps,  however,  the 


40  CHEMISTRY. 


intense  heat  of  that  seething  mass  which  pours  its  volcanic 
torrents  millions  of  miles  out  from  the  surface  is  sufficient  to 
keep  in  a  state  of  decomposition  molecules  such  as  we  know 
here,  and  even  the  elementary  atoms  which  are  at  present 
undecomposable  by  our  processes. 

Atoms  and  Molecules  Manifest  Chemical  Affinity. 

But,  to  the  chemist,  atoms,  molecules  and  masses  possess  an 
interest  of  another  kind.  Each  atom  and  each  molecule  is 
endowed  with  an  invisible,  occult  power  called  chemical 
affinity.  This  power  acts  like  an  unseen  spirit  possessed  of 
likes  and  dislikes.  By  reason  of  it  an  atom  of  hydrogen, 
for  example,  instantly  binds  itself  to  an  atom  of  chlorine 
whenever  opportunity  offers,  but  will  never,  even  under  the 
most  favorable  circumstances,  combine  with  an  atom  of  gold. 

Finally,  this  attractive  force  is  a  kind  of  energy  of  which 
no  true  explanation  can  be  offered.  All  that  human  beings 
can  do  is  to  attentively  study  it  as  it  manifests  itself  in  the 
relations  of  elementary  substances  and  compound  substances 
one  toward  another.  Indeed  one  of  the  principal  offices  of 
chemistry  is  to  study  these  relationships  as  they  develop.  It 
is  the  multitude  of  possible  relationships  and  actions  of  which 
the  numberless  substances  known  are  capable  that  gives  to 
chemistry  its  great  scope  and  variety,  and  that  makes  it  such  a 
vast  field  for  experiment,  for  discovery  of  facts,  and  for 
industrial  application  of  them. 


READING  REFERENCES. 
Atoms  and  Molecules. 

Barker.  G.  P.—  Amer.  Chemist.     Nov.  1876.     vii,  p.  164. 
Stoney,  Johnstone.— Phil.  Mag.     xxxvi,  p.  132. 
Clerk-Maxwell,  J._ Encyclopedia  Britannica,  article  Atoms. 

— Theory  of  Heat.     New  York.     1872. 
Thomson,  Sir  Wm.— Nature.     Mch.     1870. 

Tait,  P.  G-. — Recent  Advances  in  Physical  Science.  London   1876.  p.  283. 
Mayer,  A.  M.— Lecture  Notes  on  Physics,     p.  52. 
Cooke,  J.  P.— The  New  Chemistry.     New  York.     pp.  29-43. 
• American  Cyclopedia,  article  Molecule. 


HOW   CHEMICAL  AFFINITY   WORKS.  41 


VIII. 

HOW  CHEMICAL  AFFINITY  WORKS. 

l|T  is  an  interesting  fact  that  elements  and  compounds 
manifest  an  exceedingly  great  variety  of  tenden- 
cies to  combination.  Fragments  of  matter,  so 
small  that  no  eye  perceives  them,  have,  wrapped  up 
in  themselves,  a  multitude  of  determinate  powers.  A  given 
atom,  as  of  lead  for  example,  will  very  readily  combine  with 
oxygen  and  with  some  other  substances,  but  it  seems  to  abso- 
lutely refuse  to  combine  with  nitrogen.  So  hydrogen  will  com- 
bine very  readily  with  chlorine  and  with  many  other  elements, 
but  it  refuses  to  form  any  union  with  silver  and  with  many 
other  elementary  substances.  It  cannot  be  called  a  whim  that 
determines  the  kind  of  element  or  its  amount  that  a  certain 
substance  will  combine  with,  though  the  likes  and  dislikes  of 
atoms  are  in  this  respect  exceedingly  marked  and  even  incom- 
prehensible. But  however  impossible  it  may  be  to  explain 
an  element's  friendly  or  unfriendly  deportment  toward 
another,  it  is  possible  in  each  case  to  learn  the  facts  with  cer- 
tainty ;  for  each  atom  possesses  its  true  individuality,  and  is 
always  constant  and  consistent  in  its  affinities  and  hates. 

It  is  the  purpose  of  this  chapter  to  present  in  an  orderly 
manner  some  of  the  peculiarities  of  this  mysterious  power  of 
chemical  affinity. 

First.    Each   Kind  of  Atom   Has   Its  Peculiar 
Chemical  Affinities, 

Chemical  affinity  seems  to  reside  within  the  atom  as  a  per- 
manent, ever  present  and  guiding  energy.  Thus  while  iron 
oxidizes  readily — that  is,  manifests  under  a  multitude  of  com- 
mon conditions  a  willingness  to  combine  with  oxygen  and 
form  a  new  compound  called  oxide  of  iron,  and  well  known 
under  the  name  of  iron-rust — gold,  on  the  other  hand,  oxidizes 


42  CHEMISTRY. 


unwillingly ;  indeed  in  order  to  get  it  to  combine  with  oxygen 
it  must  be  coaxed  by  means  of  circuitous  and  carefully  planned 
devices.  But  these  atoms  are  always  consistent  in  their 
action,  for  iron  under  any  and  every  condition  oxidizes  more 
readily  than  gold  does. 

Second.   Chemical  Affinity  Acts  Only  Under  Favor- 
able Conditions. 

While  chemical  action  often  works  with  most  intense  energy 
it  does  so  only  when  certain  outside  and  incidental  conditions 
are  favorable.  Thus  carbon  has  under  certain  conditions  an 
affinity  for  oxygen,  and  manifests  its  tendency  to  combination 
with  an  intensity  that  is  scarcely  surpassed.  In  order,  how- 
ever, to  awaken  and  vivify  the  dormant  inclination  it  must  be 
stimulated  by  certain  definite  and  favorable  conditions.  The 
most  important  of  these  conditions  is  a  certain  amount  of 
warmth.  The  stores  of  fuel  in  our  cellars — the  coal  and  the 
wood  and  all  other  combustible  things — are  surrounded  by 
great  quantities  of  oxygen,  wrhich  winds  its  way,  with  every 
slightest  stir  of  the  mobile  air,  in  and  out  through  all  the 
crevices  that  the  fuel  affords,  passing  continually  in  the 
immediate  neighborhood  of  ample  quantities  of  atoms  of 
carbon.  But  it  does  not  ordinarily  unite  with  them.  Sub- 
ject the  whole  or  any  portion  of  these  combustible  things  to 
a,  slight  rise  in  temperature — then  the  atoms  of  oxygen  and 
the  atoms  of  carbon  seem  to  arouse  themselves  from  repose  : 
they  unite  in  friendly  and  firm  grasp,  and  what  is  called 
chemical  union  takes  place. 

To  the  ordinary  observer  the  heat  that  is  produced  is  the 
most  notable  sign  of  this  kind  of  combination.  The  chemist, 
however,  discovers  a  yet  more  conclusive  evidence,  for  he 
finds  that  several  kinds  of  new  molecules  have  been  produced  ; 
one  of  these  kinds,  for  example,  is  expressible  by  the  name 
carbon  dioxide  and  by  the  formula  CO2 .  Evidently  this  for- 
mula means  that  each  atom  of  carbon  has  united  with  two 
atoms  of  oxygen.  In  this  familiar  example  heat  is  the  agency 


HOW   CHEMICAL  AFFINITY    WORKS.  43 


that  stimulates  the  atoms  to  a  display  of  the  chemical  force 
that  previously  was  slumbering  within  them. 

Light,  and  the  electric  current,  and  the  vital  forces  of  ani- 
mals and  plants,  though  acting  in  a  manner  less  familiar  to  us, 
are  energizers  of  chemical  affinity,  and  all  have  their  proper 
influence  to  make  atoms  join  in  union  ;  indeed  in  some  cases 
they  make  atoms  burst  from  each  other's  bonds  and  fly  away 
to  more  congenial  conditions. 


Third.     Each   Atom   Has  Certain  General   Numer- 
ical Preferences. 

The  chemist  also  recognizes  each  atom  as  possessing  certain 
peculiar  numerical  preferences  in  its  combinations  ;  a  mani- 
festation of  chemical  affinity  called  equivalence,  or  atom-fixing 
power.  Thus  when  carbon  burns  in  a  stove,  by  reason  of  the 
air  passing  by  it  on  the  wray  to  the  chimney,  it  seizes  upon 
some  of  the  oxygen  atoms  and  binds  a  definite  number  of 
them  to  itself.  If  there  is  much  air,  each  atom  of  carbon,  of 
the  millions  present,  picks  out  two  atoms  of  oxygen  from  the 
air ;  if  there  is  but  little  air,  each  atom  of  carbon  has 
to  be  satisfied  with  one  atom  of  oxygen.  Now  in  these  two 
cases,  of  course,  different  substances  are  formed.  The  first, 
whose  composition  is  represented  by  the  formula  CO2,  has 
already  been  spoken  of  as  carbon  dioxide.  To  the  other, 
whose  composition  is  represented  by  the  formula  CO,  is  ap- 
plied the  name  carbon  monoxide.  Here,  then,  we  see  that 
the  same  atom  may  sometimes  combine  with  two  atoms  of 
oxygen  and  sometimes  with  only  one. 

Further,  the  chemist  knows  four  simple  and  familiar  com- 
pounds whose  molecules  illustrate  very  strikingly  the  differ- 
ence of  equivalence  of  different  atoms.  These  compounds  are 
the  following  : 

Hydrochloric  acid         (Hydric  chloride),         HCI  or  H— Cl 

IT-  ) 
Water  (Hydric  oxide),  H20  or  J-  0 


44  CHEMISTRY. 


Ammonia  gas  (Hydric  nitride), 


H-) 

H3X  or  H—  J.  S 
H-J 


H-] 

Marsh  gas  (Hydric  carbide),          H4C  or  H —  I 

H — 
H— 

It  has  been  found  advisable  to  adopt  the  atom  of  hydro- 
gen as  the  standard  of  equivalence  or  atom-fixing  power. 
It  is  plain  that  by  this  method  of  comparison  the  atom 
chlorine  may  be  said  to  have  the  equivalence  one,  since  it 
combines  with  one  atom  of  hydrogen.  And  so  the  atom 
oxygen  may  be  said  to  have  the  equivalence  two,  since  it 
combines  with  two  atoms  of  hydrogen.  And  the  atom 
nitrogen  may  be  said  to  have  the  equivalence  three,  since  it 
combines  with  three  atoms  of  hydrogen.  And  the  atom 
carbon  may  be  said  to  have  the  equivalence  four,  since  it 
combines  with  four  atoms  of  hydrogen. 

The  language  of  chemistry  sometimes  presents  the  same 
observed  facts,  in  a  slightly  different  form,  somewhat  as  fol- 
lows: Chlorine  is  said  to  have  one  point  of  attraction  and  is 
called  a  monad  (a  term  derived  from  the  Greek  word  \iovdc, 
monas,  a  unit).  Oxygen  is  said  to  have  two  points  of 
attraction  and  is  called  a  dyad  (a  term  derived  from  the 
Greek  word  6v dg,  clyas,  two).  Nitrogen  is  said  to  have  three 
points  of  attraction  and  is  called  a  triad  (a  term  derived 
from  the  Greek  word  rotdg,  trios,  a  group  of  three).  Car- 
bon is  said  to  have  four  points  of  attraction  and  is  called  a 
tetrad  (a  term  derived  from  the  Greek  word  rrTpdg,  tetras, 
four). 

While  hydrogen  as  the  basis  of  the  system  has  the  uniform 
equivalence  one,  and  is  always  a  monad,  and  oxygen  its  close 
friend  and  ally  lias  always  the  equivalence  two,  and  is 
always  a  dyad,  most  other  elements  have  some  variety  of 
equivalence.  Thus  chlorine  has  at  different  times  different 
equivalences,  sometimes  one,  sometimes  three,  or  five,  or 
seven.  So  nitrogen  has  at  different  times  the  different 


HOW  CHEMICAL  AFFINITY   WORKS.  45 

equivalences,  one,  three,  Jive.     So  carbon  has  sometimes  an 
equivalence  two,  sometimes  four. 


Fourth.    Each  Atom  Has  Certain  Special  Numer- 
ical Preferences. 

Careful  experiment  has  shown  that  the  elementary  sub* 
stances  unite  in  fixed  proportions  by  weight.  Thus  one 
ounce  of  hydrogen  unites  with  almost  exactly  thirty-five  and 
a  half  ounces  of  chlorine  to  form  hydrochloric  acid;  and  one 
ounce  of  hydrogen  unites  with  almost  exactly  eighty  ounces 
of  bromine  to  form  bydrobromic  acid;  and  one  ounce  of 
hydrogen  unites  with  almost  exactly  one  hundred  and  twenty- 
seven  ounces  of  iodine  to  form  hydriodic  acid. 

Again,  twenty-three  grains  of  sodium  unite  with  thirty- 
five  and  a  half  grains  of  chlorine  to  form  sodic  chloride; 
and  twenty-three  grains  of  sodium  unite  with  eighty  grains 
of  bromine  to  form  sodic  bromide;  and  twenty-three  grains 
of  sodium  unite  with  one  hundred  and  twenty-seven  grains 
of  iodine  to  form  sodic  iodide. 

Now  these  numbers — 

1.  for  hydrogen, 

23.  "     sodium, 

35.5  "     chlorine, 

80.  "     bromine, 

127.  "     iodine, 

are  fixed  and  constant  numbers,  and  are  largely  used  in 
chemical  computations. 

They  are  called  combining  numbers,  for  such  indeed  they 
are;  they  are  also  called  atomic  weights,  and  they  are  sup- 
posed to  represent  the  relative  weights  of  single  atoms  of  the 
substances  mentioned. 

Careful  chemical  study  of  the  way  in  which  atoms 
combine  has  developed  the  following  as  a  fundamental  law 
of  nature.  In  the  same  chemical  compound  there  are  always 
the  same  kind  and  number  of  elementary  atoms,  and  these 


46  CHEMISTRY. 


atoms  are  united  in  fixed  proportions  by  weight.  This  law 
is  a  formal  statement  of  facts  similar  to  those  just  referred 
to  in  this  and  the  preceding  topic.  It  does  not  therefore 
seem  to  call  for  further  explanation  at  this  point. 

Fifth.      Chemical    Changes    Neither    Create    nor 
Destroy  Matter. 

When  chemical  changes  are  produced  by  reason  of  the 
action  of  chemical  affinity,  there  is  never  either  gain  in 
weight  or  loss  in  weight.  In  other  words  there  is  no 
creation  of  matter  and  no  destruction  of  it.  In  former 
times,  people  who  observed  the  disappearance  of  solid  mat- 
ter when  charcoal  burns  thought  that  the  substance  was 
destroyed — partly  if  not  wholly.  The  modern  chemist  finds, 
however,  that  the  carbon  is  only  turned  into  the  form  of  an 
invisible  gas,  and  that  by  the  use  of  appropriate  appliances 
he  can  find  the  weight  of  this  gas  and  compare  it  with 
that  of  the  carbon  producing  it.  In  the  combustion  of  car- 
bon the  chemical  change  is  represented  by  the  following 
equation : 

C  +  02  C02 

One  atom  of  Two  atoms  of  One  molecule  of 

Carbon  Oxygen  Carbon  dioxide. 

12  32  44 

parts  by  weight.  parts  by  weight.  parts  by  weight. 


44  44 

This  equation  means  that  the  chemist  has  discovered,  by 
careful  experiments,  that  when  any  twelve  parts  by  weight 
of  carbon — say  twelve  pounds — are  completely  burned,  they 
always  unite  with  thirty-two  corresponding  parts  of  oxygen 
(in  this  case  thirty-two  pounds),  and  they  produce  forty-four 
parts  by  weight  of  carbon  dioxide  (in  this  case  forty-four 
pounds). 

And  so  in  all  chemical  changes;  the  substances  taking  part 
— whether  solid,  liquid  or  gaseous — may  be  weighed,  and  the 


110  W    CHEMICAL  AFFINITY   WORKS.  47 


sum  of  the  weights  of  all  the   matters  finally  produced  is 
just  equal  to  the  sum  of  the  weights  of  the  original  factors. 


Sixth.    Chemical    Changes    Produce    Striking 
Results. 

So  far  as  our  present  knowledge  goes  each  of  the  atoms 
appears  to  be  fixed  and  unchangeable  and  to  possess  through 
all  its  varied  combinations  an  inherent  character  which 
belongs  to  it,  and  which  no  human  being  at  present  knows 
how  to  alter.  It  is  true,  however,  that  the  opinion  seems  to 
be  gaining  ground  that  the  elementary  atoms  are  probably 
themselves  compounds  whose  parts  are  very  firmly  bound 
together ;  compounds  which  may  in  future  be  decomposed. 
Whatever  may  be  the  truth  on  this  subject,  it  is  recognized 
that  when  the  atoms  at  present  accepted  as  elementary  unite  to 
build  up  either  simple  or  complex  molecules,  the  various  orig- 
inal atomic  characters  are  so  blended  and  balanced  and  re-en- 
forced as  to  afford  in  the  molecular  product  an  entirely  new 
and  unexpected  set  of  properties.  An  example  of  this  latter 
fact  is  found  in  the  union  of  copper,  sulphur,  oxygen  and 
hydrogen.  These  substances  may  combine  to  form  a  mole- 
cule which  is  called  cupric  sulphate,  which  has  the  compo- 
sition expressed  by  the  formula 

CuS045H20. 

Of  the  constituents  of  this  molecule,  copper  is  red,  sulphur  is 
yellow,  oxygen  is  colorless,  hydrogen  is  colorless  ;  but  when 
they  unite  the  cupric  sulphate  formed  is  blue — that  is,  its  color 
is  not  that  of  either  of  its  constituents,  nor  is  it  intermediate 
between  them.  There  is  simply  a  new  and  unexpected  result, 
and  one  which  in  the  present  state  of  knowledge  cannot  be 
explained;  it  can  merely  be  recorded.  And  this  example  is 
only  one  of  a  myriad.  Throughout  nature  chemical  changes 
most  marked — and  to  human  thought  unexpected — arise  from 
the  union  of  familiar  elementary  substances. 


48  CHEMISTRY. 


Seventh.  Chemical  Changes  are  Often  Attended  by 
Displays  of  Force. 

In  many  chemical  changes  the  union  of  the  atoms  is 
attended  with  the  production  of  heat,  or  electricity,  or  some 
other  form  of  energy.  Now  it  is  a  law  derived  from  mod- 
ern discoveries  that  the  amount  of  energy  given  out  by  any 
chemical  union  is  fixed  and  invariable,  and  that  it  is  just  the 
same  in  amount  as  the  quantity  of  that  kind  of  energy  that 
is  absorbed  when  such  chemical  action  is  reversed. 


The  Modern  Atomic  Theory. 

The  same  chemical  study  which  has  developed  the  truth 
of  the  facts  already  stated  in  this  chapter  has  also  given  rise 
to  the  modern  atomic  theory.  The  chemist  is  constrained  to 
believe  that  matter  is  composed  of  ultimate  particles,  as  yet 
undivided,  called  atoms.  While  these  atoms  are  invisible  to 
mortal  eye,  even  with  the  help  of  the  finest  known  optical 
appliances,  yet  when  their  existence  is  once  admitted  this 
admission  affords  an  explanation  that  is  a  satisfactory  one, 
and  indeed  the  only  one  that  harmonizes  with  the  multitude 
of  observed  chemical  and  physical  laws. 

This  atomic  theory,  in  its  essential  features,  was  suggested 
in  the  early  part  of  this  century  by  Dr.  John  Dalton,  who 
was  a  teacher  of  mathematics  in  Manchester,  England,  and 
who  died  as  recently  as  in  1844.  Dalton  found  recreation  in 
chemical  experiments,  and  the  mathematical  turn  of  his  mind 
led  him  to  express  the  results  of  his  chemical  analyses  in  a 
new  numerical  form.  Thus,  previous  to  his  time,  it  had  been 
customary  to  express  the  composition  of  all  substances  in 
the  ordinary  percentage  form.  Now  Dalton  found  that 
when  some  special  weight  is  adopted  as  the  unit  a  variety  of 
previously  concealed  facts  are  revealed.  The  idea  to  be  here 
conveyed  is  partially,  but  perhaps  sufficiently,  expressed  by 
the  following  examples  derived  from  the  two  compounds  of 
carbon  already  referred  to: 


FIG  3.-John  Dalton.    Born  at  Eaglesfleld,  England,  Sept.  5,  1766 ;  died  July  27, 1844. 

(49) 


50  CHEMISTRY. 


Composition  of  the  Two  Compounds  of  Carbon  and 
Oxygen. 


EXPRESSED    IN  PER    CENTS. 


Carbon  Monoxide  (CO).  Carbon  Dioxide  (COJ. 

Carbon,         43  per  cent.  27  per  cent. 

Oxygen,        57  per  cent.  73  per  cent. 

100  100 


EXPRESSED  IN  DALTON'S  FORM. 

Carbon  Monoxide  (CO). 
Carbon,    12  parts  by  weight. 
Oxygen,  16  parts  by  weight. 

28 

Carbon  Dioxide  (CO^). 
12  parts  by  weight. 
32  parts  by  weight. 

44 

In  Dalton's  expression  it  is  at  once  evident  that,  as  com- 
pared with  the  weight  of  carbon,  the  amount  of  oxygen  in 
carbon  dioxide  is  exactly  twice  what  it  is  in  carbon  mo- 
noxide; but  to  the  ordinary  un mathematical  mind  the  per  cent- 
age  statement  conceals  this  fact.  Dalton's  experiments  with 
still  other  compounds  gave  him  results  showing  a  simplicity 
of  relationships  similar  to  that  obtained  from  the  carbon  com- 
pounds just  referred  to.  To  his  mind  these  facts  suggested 
immediately  the  idea  that  an  elementary  substance  is  made 
up  of  atoms  each  of  a  determinate  weight,  and  that  these 
atoms  combine  by  wholes  and  not  by  fractional  parts,  and 
that  although  it  is  impossible  to  actually  weigh  any  atom 
separately,  yet  the  weight  ratios  of  a  multitude  of  them  that 
combine  as  wholes  express  at  once  the  weight  ratios  of  the 
atoms  themselves.  He  thus  got  the  idea  of  atomic  weights 
and  constructed  the  first  table  of  them.  Since  Dalton's  first 


HOW  CHEMICAL  AFFINITY   WORKS.  51 

declaration  of  his  atomic  theory,  the  combining  numbers  of 
the  different  atoms  have  been  studied  by  chemists  with  the 
most  thoughtful  care  and  the  most  painstaking  methods 
known  to  modern  science;  and  tables  have  been  constructed 
showing  the  combining  numbers  which  are  believed  also  to 
be  the  true  atomic  weights  for  all  the  various  elements  thus 
far  recognized. 


READING  REFERENCES. 

Atomic  Constitution  of  Bodies. 

Saint-Venant. — Jour,  of  Chem.  Soc.  of  London,     xxx,  pt  II,  472. 
Atomic  Philosophy. 

Amer.  Chemist,     iii,  326. 

Atomic  Theory. 

Williamson,  A.  W.  (and  others.) — Jour,  of  Chem.  Soc.  of  London,     xxii, 
328,  433. 

Wurtz,  Ad. — The  Atomic  Theory.     New  York.     1881. 

Atomic  Volumes,  Etc. 

Avogadro. — Annales  de  Chimie  et  de  Physique.      3  Se'r.     xiv,  330, 
xxix,  248. 

Atoms,  Vortex  Theory  of 

Thomson,  Sir  Wm.— Phil.  Mag.     1867. 

Thomson,  J.  J. — Science,     iii,  289. 

Tait,  P.  G. — Recent  Advances  in   Physical  Sc'ence.     London.     1876. 

p.  283. 
Atomic  Weights,  Dalton's  First  Table  of 

Roscoe,  H.  E. — Chem.  News,     xxx,  266. 
Chemical  Operations,  Calculus  of 

Brodie,  B.  C. — Jour,  of  Chem.  Soc.  of  London,     xxi,  367. 
Dalton,  John 

Henry,  W.  C. — Life  of  Dalton.     London.     1854. 
Definite  Proportions,  Variability  in  Law  of, 

Boutlerow. — Silliman's  Journal.     3d  Ser.     xxvi,  63. 

Cooke,  J.  P. — loc.  cit.     310. 

Equivalents  of  the  Elements. 

Pumas,  J. — AnnaJes  de  Chiraie  et  de  Physique.     3  Se'r.     lv,  129. 


53  CHEMISTRY. 


Energy. 

Stewart,  Balfour. — The  Conservation  of  Energy.     New  York.     1874. 
Tait,  P.  G. — Recent  Advances  in  Ph}rsical  Science.     London.     187G. 
Encyclopedia  Britannica.     vol.  viii. 

Gaseous  and  Liquid  States  of  Matter. 

Andrews,  T. — Jour,  of  Chem.  Soc.  of  London,     xxiii,  74;  xxx,  pt.  Ii. 

159. 
Ramsey,  W. — Jour,  of  Chem.  Soc.  of  London,     xlii,  136. 

Matter,  Constitution  of 

Ditto,  A. — Annales  dc  Chimie  et  de  Physique.     5  Ser.     x,  145. 

Nomenclature  of  Salts. 

Madan,  H.  G. — Jour,  of  Chem.  Soc.  of  London,     xxiii,  22. 


HYDROGEN.  53 


IX. 

HYDROGEN. 

|HIS  substance  is  one  of  the  most  interesting  with 
which  the  chemist  has  to  deal.  On  account  of  its 
chemical  and  physical  properties,  by  reason  of  the 
many  important  compound  substances  into  which 
it  enters,  by  reason  of  the  part  it  has  played  in  the  history  of 
chemical  progress,  it  is  entitled  to  a  large  share  of  the 
student's  attention. 

Where  Hydrogen  is  Found. 

The  name  hydrogen  was  applied  to  it  some  time  later  than 
the  first  recognition  of  the  substance.  The  word  is  derived 
from  two  Greek  words^dwp,  Injdor,  water,  and  yewaw,  gennao, 
I  form  or  produce),  the  word  as  a  whole  meaning  water  former. 
In  fact  hydrogen  is  in  all  water  wherever  that  substance 
exists.  That  this  is  a  very  comprehensive  expression  appears 
when  it  is  remembered  that  the  atmosphere  always  contains 
water  diffused  through  it  in  the  form  of  invisible  vapor  even, 
before  that  vapor  is  precipitated  as  the  gentle  dew,  or  the 
crystalline  snow,  or  the  streaming  rain.  Again,  water  in 
seas  and  oceans,  lakes  and  livers,  is  the  mantle  of  nearly 
three  fourths  of  the  earth's  surface.  Every  living  being  on 
the  dry  land,  whether  animal  or  vegetable,  contains  large 
quantities  of  water  in  its  structure  :  the  blood  of  the  higher 
animals  is  nearly  eight  tenths  water. 

While  water  is  the  principal  substance  containing  hydro- 
gen, this  gas  exists  also  as  a  constituent  part  of  a  great  many 
other  solid  and  liquid  matters  found  in  the  earth. 

Why  Free  Hydrogen  is  not  Found. 

Hydrogen  scarcely  ever  exists  on  our  globe  alone — that  is, 
in  the  free  or  uncombined  condition.  Indeed  there  are  cer- 


54 


tain  definite  reasons  why  it  should  not.  These  are  based 
mainly  upon  the  very  strong  chemical  affinity  that  hydrogen 
lias  for  oxygen.  Now,  as  has  been  declared  already,  the 
latter  substance  is  the  most  abundant  element  in  nature,  and 
it  exists  in  very  large  quantities  in  our  atmosphere.  Spread 
all  over  the  surface  of  the  earth,  then,  the  free  oxygen  of  the 
air  stands  prepared  to  combine  with  hydrogen  wherever  the 
latter  may  be  liberated.  Such  combination  might  not  occur, 
it  is  true,  unless  initiated  by  influence  of  heat  or  some  flame 
of  fire  ;  but  owing  to  the  constant  agitation  of  the  air  by 
reason  of  uniform  currents  like  trade  winds,  as  well  as  those 
produced  when  the  atmosphere  is  agitated  by  violent  storms, 
any  mixture  of  hydrogen  and  oxygen  would  be  likely  soon 
to  come  into  contact  with  some  flame  or  fire,  and  so  these 
components  would  enter  into  combination.  Thus  hydrogen 
would  not  be  likely  to  remain  long  uncombined  even  were  it 
produced  in  considerable  quantity  by  natural  terrestrial 
operations. 

The  Discoverer  of  Hydrogen. 

Hydrogen  was  first  distinctly  described,  and  its  properties 
as  a  special  kind  of  gaseous  matter  clearly  pointed  out,  in  the 
year  1766,  by  an  English  chemist,  the  Honorable  Henry 
Cavendish.  This  philosopher,  the  son  of  Lord  Charles 
Cavendish,  and  the  grandson  at  once  of  the  Duke  of  Devon- 
shire and  the  Duke  of  Kent,  is  one  of  the  most  curious  char- 
acters in  the  history  of  the  natural  sciences.  He  was  of  an 
exceptionally  careful,  thorough  nnd  pains-taking  temper, 
which  well  fitted  him  for  those  scientific  pursuits  which  were 
the  prime  objects  of  his  thoughts.  Sir  Humphry  Davy  said 
of  him  :  "  The  accuracy  and  beauty  of  his  earlier  labors  have 
remained  unimpaired  amidst  the  progress  of  discovery,  and 
their  merits  have  been  illustrated  by  discussion  and  exalted 
by  time." 

In  addition  to  his  possession  of  many  special  aptitudes  for 
the  exact  studies  to  which  he  devoted  his  entire  existence, 
it  should  be  recognized  that  he  lived  at  a  period  that  was 


HYDROGEN.  55 


remarkably  favorable  to  the  pursuit  of  the  natural  sciences. 
The  times,  the  state  of  knowledge,  the  condition  of  society 
all  over  Europe  seemed  to  be  ripe  for  this  kind  of  progress, 
for  in  Scotland,  in  England,  in  France,  in  Germany,  in  Swe- 
den, there  then  appeared  experimenters  of  unsurpassed  skill, 
and  chemistry  as  a  science  had  then  its  birth  under  most  for- 
tunate auspices. 

Cavendish  was  very  peculiar  in  his  manners  and  habits, 
living  in  great  seclusion  and  retirement  and  in  the  most  sim- 
ple and  methodical  manner ;  indeed  his  oddities  attained  for 
him  the  unenviable  distinction  of  a  place  in  a  book  devoted 
to  the  lives  of  English  eccentrics.  In  that  work,  as  well  as 
in  Dr.  Wilson's  life  of  him,  are  many  amusing  anecdotes  of 
his  way  of  life.  One  most  remarkable  episode  was  his  inherit- 
ance of  wealth.  Though  poor  in  his  youth  he  was  suddenly 
made  rich  in  middle  life  by  a  bequest  whose  origin  is  scarcely 
known.  M.  Biot  neatly  described  him  as  "  le  plus  riche  de 
tous  les  savants,  et  probablement  aussi  le  plus  savant  de 
tons  les  riches."  He  lived  on  however  in  as  great  seclusion 
as  before,  his  chosen  associates  being  his  flasks  and  his  ther- 
mometers. His  millions  made  no  observable  impression  upon 
his  habits,  notwithstanding  at  his  death  they  had  made  him 
the  largest  holder  of  the  stock  of  the  Bank  of  England. 

Lord  Brougham  says  that  Cavendish  probably  uttered 
fewer  words  in  the  course  of  his  life  than  any  other  man  who 
ever  lived  to  fourscore  years,  not  at  all  excepting  the  monks 
of  La  Trappe — who  were  bound  to  perpetual  silence  except 
in  cases  of  absolute  necessity. 

Why  Hydrogen  was  not  Discovered  Earlier. 

Doubtless  those  prehistoric  men,  who  in  earliest  days  looked 
about  upon  the  face  of  the  earth  curiously  examining  their 
heritage  from  the  Creator,  were  familiar  with  water  in  its 
various  forms.  They  must  have  prized  its  bland  and  refresh- 
ing powers  and  have  learned  many  of  its  more  important  uses. 
But  the  idea  that  it  is  made  up  of  more  than  one  kind  of  sub- 


FIG.  4.-Joseph  Black,  M.D.    Born  in  Bordeaux,  in  1728 ;  died  in  Edinburgh,  Nov.  2G,  1799. 

(56) 


HYDROGEN.  57 


stance  or  matter  was  not  suspected  until  very  recent  times, 
and  not  proved  until  the  masterly  investigations  of  Caven- 
dish clearly  set  forth  the  facts. 

The  very  idea  of  a  chemical  compound—  that  is,  of  a  sub- 
stance as  made  up  of  inconceivably  small  portions  of  matter 
in  a  union  of  almost  inconceivable  intimacy,  an  idea  very 
familiar  to  students  of  the  present  day — probably  did  not  enter 
the  minds  even  of  those  profound  thinkers  who  suggested 
the  earlier  atomic  philosophies.  In  fact,  our  form  of  the 
notion  of  chemical  union  is  scarcely  more  than  a  century  old. 

Moreover,  hydrogen  is  a  gas,  and  the  notion  of  gas  is  itself 
decidedly  a  modern  one.  It  was  first  stated  in  well-defined 
form  in  the  year  1752,  by  Dr.  Joseph  Black,  professor  in 
Glasgow  and  Edinburgh.  Black  clearly  and  conclusively 
demonstrated  the  existence  of  airs  of  a  different  kind  from 
that  familiar  to  us  in  our  atmosphere.  It  is  true,  Van  Ilel- 
innnt  and  even  others,  fully  one  hundred  years  before  Black's 
time,  had  known  and  stated  more  or  less  distinctly  the  exist- 
ence of  a  gas  or  air  different  from  that  we  breathe  ;  but 
owing  to  a  variety  of  circumstances  these  wonderful  discover- 
ies were  allowed  to  lapse  into  forgetf'ulness.  Thus  the  human 
race  lost  for  a  century  much  advantageous  knowledge;  but 
probably  the  general  social  advancement  of  those  times  had 
not  then  prepared  mankind  for  the  benefits  which  the 
development  of  modern  chemistry  has  conferred  upon  the 
present  citizens  of  the  world. 

Again,  experimenting  with  gases  was  not  well  understood 
until  about  the  year  17 TO,  when  Joseph  Priestley  invented 
that  contrivance  for  manipulating  them  known  as  the  pneu- 
matic trough,  for  which  no  better  substitute  has  yet  been 
devised. 

Further,  in  water — which  has  already  been  referred  to  as 
the  most  abundant  and  widely-diffused  compound  of  hydro- 
gen— the  partner  elements  are  bound  together  by  a  chemical 
affinity  that  cannot  be  readily  overcome.  This  intensity  of 
attractive  force  between  the  constituent  elements  is  thei'e- 
fore  another  reason  why  the  true  composition  of  water  was 


CHEMISTRY. 


so  long  an  unsolved  riddle,  and  why  hydrogen  was  not  earlier 
recognized  as  a  thing  or  kind  of  matter  by  itself,  although 
in  its  principal  compound — one  of  the  most  admirable  gifts 
of  the  Creator  to  man — it  was  well-known  from  the  first  days 
of  the  human  race. 


How   Hydrogen  is  Prepared. 

Hydrogen  may  be  obtained  by  the  chemist  in  several  ways : 

First.    There  is  a  method  of  directly  tearing  the  elements 

composing  water  apart   from   each  other.     Considered  the- 


FIG.  5. — Apparatus  for  decomposition  of  water,  (by  action  of  two  cells  of  the  Bunson 
galvanic  battery)  and  for  collection  of  hydrogen  and  oxygen  gases  in  separate  receiv- 
ers over  the  two  electrodes  of  the  battery. 

oretically  this  process  is  a  most  direct  and  simple  one.  In 
order  to  realize  its  results,  however,  advantage  must  be  taken 
of  the  galvanic  current.  This  force  may  be  obtained  readily, 
it  is  true  :  thus  when  two  metals,  dipped  in  a  liquid,  are  con- 
nected by  a  wire  it  is  usually  generated.  But  no  one  knows 
fully  what  the  current  is.  The  words  galvanic  current  and 
voltaic  current  suggest  the  two  investigators,  Galvani  and 
Volta,  who  were  the  pioneers  in  this  field,  but  they  give 
nothing  that  can  be  called  an  explanation  of  the  wondrous, 
invisible,  imponderable  form  of  energy  referred  to.  It  is  a 


HYDROGEN.  50 

force  of  an  exceedingly  interesting  character  and  about  which 
a  certain  considerable  body  of  knowledge  has  been  collected. 

Among  the  variety  of  facts  known  about  it  is  that  one 
which  relates  to  water;  namely,  when  the  poles,  or  electrodes, 
of  a  suitable  galvanic  battery  are  dipped  into  a  vessel  of 
water  bubbles  of  gas  may  be  seen  to  flow  freely  from  each 
of  them.  The  gases  may  be  collected  in  a  vessel  placed  over 
the  electrodes,  but  the  experimenter  may  well  beware  of  in- 
cautiously treating  what  has  now  been  produced  ;  he  has 
obtained  a  mixture  of  oxygen  and  hydrogen  from  the  orig- 
inal water,  and  these  elements,  which  he  has  rended  apart 
from  their  more  intimate  union,  are  ready  upon  the  approach 
of  the  smallest  flame  to  rush  into  union  again,  with  extraordi- 
nary violence,  and  in  such  a  way  as  to  produce  a  tremendous 
explosion.  In  the  act  of  this  explosion,  therefore,  water  is 
again  produced,  first  as  expansive  vapor,  then  condensible 
back  to  the  liquid  drops  whence  it  came. 

If  however  the  product  from  each  electrode  is  collected  by 
itself  in  a  separate  tube,  the  one  gas  is  found  to  be  very  differ- 
ent from  the  other.  The  one  is  found  to  be  hydrogen,  the 
other  oxygen.  In  accordance  with  the  formula  H2O — which 
it  has  before  been  stated  represents  the  composition  of  water 
— the  hydrogen  is  found  to  be  given  off  in  a  bulk  or  volume 
that  is  twice  as  great  as  that  of  the  oxygen  obtained  at  the 
same  time  from  the  same  amount  of  water. 

Second.  Hydrogen  may  be  obtained  by  bringing  into  con- 
tact with  water,  under  proper  conditions,  certain  substances 
that  have  a  very  strong  affinity  for  its  oxygen  and  at  the 
same  time  but  little  affinity  for  its  hydrogen.  Now  every 
one  is  familiar  with  the  fact  that  iron  rusts  readily  in  the 
air.  The  chemist  can  demonstrate  that  this  rust  is  a  com- 
pound of  iron  and  oxygen.  The  union  of  these  elements 
under  ordinary  conditions  suggests  at  once  that  that  union 
arises  from  an  affinity  between  the  iron  and  the  oxygen. 
This  affinity  is  much  greater  at  high  temperatures,  for  it  is 
well  known  that  iron  rusts  more  violently  when  subjected  to 
heat.  These  facts,  then,  are  made  use  of  for  the  purpose  of 


60 


CHEMISTRY. 


withdrawing  oxygen  from  water  and  thus  forcing  the  hydro- 
gen out  in  the  free  or  uncombined  condition,  so  that  it  may 
be  obtained  and  experimented  upon. 

To  produce  hydrogen  by  this  method  there  must  be  pro- 
vided a  long  iron  pipe  which  passes  through  a  hot  furnace; 
the  pipe  should  contain  fragments  of  iron,  such  as  iron  turn- 
ings, or  iron  filings,  or  pieces  of  iron  wire.  Then  a  current 
of  steam  must  be  passed  through  the  pipe.  The  iron  be- 


FIG.  6. — Apparatus  for  preparation  of  hydrogen  gas.  Steam,  ^enerated  in  the 
small  retort,  is  conveyed  through  the  tube  placed  in  the  gas-furnace;  iron  turnings 
within  the  tube  being  highly  heated,  decompose  the  water-vapor,  which  thereby 
evolves  hydrogen.  The  liberated  gas  is  collected  in  the  little  bell-glass. 

comes  red  hot,  and  under  these  circumstances  manifests  more 
affinity  for  the  oxygen  of  the  steam  than  the  hydrogen  does. 
The  iron  then  grasps  the  oxygen  and  holds  it  fast.  As  a 
result  a  peculiar  kind  of  oxide  of  iron  of  a  black  color  is 
produced.  Its  chemical  formula  is  Fe3O4,  and  it  is  cnlled  by 
chemists  ferroso-ferric  oxide.  The  iron  has  now  taken  the 
place,  as  a  partner  of  the  oxygen,  that  the  hydrogen  formerly 
had.  The  hydrogen  is  thus  cast  out  from  its  combination 
and  is  set  free  as  an  uncombined  gas,  in  which  liberated  con- 
dition it  is  expelled  at  the  end  of  the  tube.  The  chemical 
action  between  the  iron  and  the  steam  may  be  represented 
by  the  following  equation ; 


HYDROGEN.  61 


Fe3 

r-          4H,0 

Fe304            -| 

4H3 

Three  atoms  of 

Four  molecules  of 

One  molecule  of 

Four  molecules  of 

Iron, 

Water, 

Fcrroso-ferric  oxide, 

Hydrogen, 

1G8 

72 

232 

8 

parts  by  weight. 

parts  by  weight. 

parts  by  weight. 

parts  by  weight. 

240  210 

The  gas  produced  as  just  described  may  bo  collected  by 
adjusting  a  suitable  tube  in  connection  with  the  pipe  con- 
taining the  iron.  When  the  gas  is  examined  it  is  found  to 
be  in  fact  hydrogen.  It  will  burn  with  a  blue  flame  and 
perform  all  the  various  actions  that  acknowledged  hydrogen 
will. 

Third.  There  are  other  metals,  not  used  in  the  ordinary 
arts  and  trades  but  still  familiar  to  the  chemist,  which  have 
far  greater  affinity  for  oxygen  than  iron  has.  The  metal 
called  sodium  is  one  of  these.  Its  affinity  for  oxygen  is  so 
great  that  it  cannot  be  long  preserved  in  the  open  air  ;  a 
block  or  lump  of  it,  if  exposed  to  the  air,  gradually  turns  to 
a  mass  of  rust  of  sodium — that  is,  oxide  of  sodium.  This 
metal,  therefore,  is  preserved  by  the  chemist  in  tightly  closed 
bottles  or  else  under  a  layer  of  petroleum  oil.  The  oil  keeps 
the  air  away  from  the  metal;  moreover  the  oil  contains  no 
oxygen  in  its  composition,  as  many  other  liquids  do.  This 
metal,  sodium,  though  heavier  than  the  oil,  is  lighter  than 
water.  If  thrown  upon  water  it  floats.  But,  by  virtue  of 
its  intense  affinity  for  oxygen,  it  at  the  same  time  decomposes 
the  water.  It  draws  the  oxygen  to  itself  and  it  liberates  the 
hydrogen.  Some  chemical  skill  is  requisite  in  the  perform- 
ance of  this  apparently  simple  experiment,  for  occasionally 
the  violent  affinities  involved  set  the  sodium  and  the  hydro- 
gen on  fire,  and  give  rise  to  dangerous  explosions.  When 
properly  conducted,  however,  the  hydrogen  from  this  process 
may  be  collected  in  a  vessel  and  its  various  characteristics 
displayed.* 

Fourth.  The  most  common  way  of  producing  hydrogen 
is  by  bringing  together  sulphuric  acid  and  zinc. 

*  Appleton's  Young  Chemist,  Philadelphia,  Cowperthwait  &  Co-    pp.  26,  27,  28, 


62 


CHEMISTRY. 


The   chemical   change   is   represented    by   the   following 
equation : 

Zn  -f  H2SO4  ZnSO4  +  H2 

One  atom  of 

Zinc, 
65 

parts  by  weight. 


One  molecule  of 

Sulphuric  acid, 
98 

parts  by  weight. 


One  molecule  of 

Zinc  sulphate, 
161 

parts  by  weight. 


One  molecule  of 

Hydrogen, 
2 

parts  by  weight. 


163 


163 


The  zinc  has  affinity  for  the  compound  radicle  SO4 ,  known 
as  the  sulphuric  acid  radicle,  and  it  is  plain  that  by  reason 
of  its  affinities  the  zinc  takes  the  place  of  the  hydrogen — or 
the  place  which  the  hydrogen  formerly  held  as  related  to 
the  sulphuric  acid  radicle,  SO4 — and  that  the  hydrogen, 

^  thereby  left  with- 

O  out  any  thing  to 

combine  with,  ap- 
pears as  a  free  and 
uncombined  sub- 
stance. The  hy- 
drogen produced 
by  this  method  can 
be  readily  collect- 
ed and  examined. 
Perhaps  it  ought 
to  be  stated  that 
neither  of  the  proc- 
esses thus  far  ex- 
plained is  likely 
to  yield  hydrogen  in  an  absolutely  pure  condition.  The  va- 
rious substances  used  are  likely  themselves  to  contain,  asso- 
ciated with  them,  small  amounts  of  other  substances  which 
give  some  impurity  to  the  gas  evolved. 

Powers  and  Properties  Manifested  by  Hydrogen. 

Hydrogen  has  been  seen,  from  the  explanation  already 
given,  to  be  a  gas.  Down  to  within  a  few  years  it  resisted 
all  attempts  to  liquefy  it.  Chemists  submitted  it  to  intense 


FIG.  7.— Apparatus  for  production  of  hydrogen  by  ac- 
tion of  sulphuric  acid  on  zinc,  and  for  collection  of  the 
gas  in  a  receiver. 


HYDROGEN.  63 


cold  and  enormous  pressure,  and  to  both  these  influences  at 
the  same  time,  but  without  avail.  Within  a  few  years,  how- 
ever, by  use  of  ampler  resources  and  contrivances  for  the 
application  of  these  condensing  agencies,  it  has  been  brought 
down  to  the  liquid  and  perhaps  even  to  the  solid  state. 

As  a  gas  it  is  colorless,  odorless,  tasteless. 

Bulk  for  bulk,  it  is  the  lightest  substance  known  in  nature. 
Thus  a  quart  of  atmospheric  air,  light  as  it  is,  weighs  over  four- 
teen times  as  much  as  a  quart  of  hydrogen.  A  cubic  inch  of 
gold  weighs  more  than  two  hundred  thousand  times  as  much 
as  a  cubic  inch  of  hydrogen.  This  lightness  is  properly 
illustrated  by  inflating  a  soap  bubble  with  hydrogen  rather 
than  with  air.  When  soap  bubbles  are  filled  with  air  they 
fall,  unless,  indeed,  carried  upward  by  a  temporary  current; 
but  when  filled  with  hydrogen  they  invariably  rise  with  great 
rapidity.  By  reason  of  this  great  lightness  hydrogen  was 
formerly  used  for  the  inflating  of  balloons,  but  at  the  present 
day  illuminating  gas  is  so  much  cheaper  that  the  latter  is 
generally  used,  although  it  is  much  heavier  than  hydrogen. 

Diffusive  Power  of  Hydrogen  Gas. 

It  is  not  inappropriate  to  call  attention  here  to  certain 
interesting  relations  th.'it  hydrogen  manifests  toward  gases 
and  solids.  Thus  hydrogen  possesses  to  a  marked  degree 
that  curious  facility  of  passing  into  and  permeating  other 
gases  which  is  spoken  of  as  its  diffusive  power.  True,  this 
power  is  possessed  by  all  gases  to  a  certain  extent;  but  in 
rapidity  of  action  none  approach  hydrogen.  As  early  as 
1825  a  German  chemist  named  Dobereiner  announced  his 
observations  of  this  power.  He  noticed  that  upon  collecting 
some  hydrogen  in  a  cracked  jar,  placed  in  a  pneumatic  trough, 
the  hydrogen  leaked  out  into  the  air  more  rapidly  than  the 
air  went  in.  So  that  in  fact  the  water  of  the  \rough  rose  on 
the  inside  of  the  jar.  It  has  been  since  discovered  that 
when  almost  any  two  gases  whatsoever,  if  only  of  different 
densities,  are  separated  by  a  partition  having  fine  cracks  or 


64  CHEMISTRY. 


holes  in  it,  the  lighter  gas  always  moves  out  into  the  heavier 
one  more  rapidly  than  the  heavier  gas  moves  in.  As  hydro- 
gen is  the  lightest  of  all,  of  course  it  diffuses  into  other  gases 
with  the  greatest  rapidity. 

In  liquids  hydrogen  does  not  ordinarily  dissolve  in  any 
considerable  quantity. 

With  solids,  however,  it  displays  some  properties  that  are 
well-nigh  incredible.  Thus  it  has  a  very  curious  aptitude 
for  passing  into  the  very  interior  of  certain  solid  metals. 
The  white,  compact,  solid  metal  palladium,  although  it  has 
no  visible  pores,  has  the  power  of  swallowing  up  into  itself, 
in  some  mysterious  way,  nearly  a  thousand  times  its  bulk 
of  this  gas;  and,  again,  a  thin  sheet  of  this  same  solid  metal, 
air-tight  to  all  appearances,  allows  hydrogen  to  pass  through 
it  as  easily  as  a  sieve  does  water. 

The    Most    Interesting   Chemical    Property  of 
Hydrogen. 

T5y  all  means  the  most  interesting  chemical  property  of 
hydrogen  is  its  power  to  unite  with  oxygen.  When  it  does 
so  unite  all  the  phenomena  of  combustion  appear.  These 
phenomena  are  generally  the  production  of  heat,  light,  flame, 
and  the  formation  of  some  new  chemical  compound.  So,  then, 
when  hydrogen  unites  writh  oxygen  it  burns,  it  gives  out 
light  (although  that  light  is  of  but  feeble  intensity),  it  gives 
out  an  enormous  quantity  of  heat,  it  forms  an  oxidized  prod- 
uct. This  product  is  water,  but  water  that — owing  to  the 
great  heat  of  the  combustion — is  raised  to  the  form  of  invis- 
ible vapor.  When,  however,  a  jet  of  hydrogen  gas  is  burned 
under  a  bright  but  cool  bell-glass,  the  deposit  of  mist 
quickly  formed  on  the  inside  of  the  glass  shows  that  the 
vapor  produced  by  combustion  has  now  condensed  on  the 
bell  to  minute  liquid  drops. 

In  the  matter  of  the  heat  involved  hydrogen  has  the  dis- 
tinction of  being  above  every  other  substance.  One  pound 
of  hydrogen  when  burned  under  favorable  conditions  evolves 


PLATE  II.— Bottling  natural  mineral  water.     (See  Chap.  XVI.) 


HYDROGEN. 


65 


heat  enough  to  raise  tJrirty-four  thousand,  four  hundred 
and  sixty-two  pounds  of  water  from  zero  centigrade  to 
one  degree  centigrade,  or 
nearly  the  same  as  from 
32  degrees  Fahrenheit 
to  34  degrees  Fahrenheit. 
This  expression  of  the  calo- 
rific power  of  hydrogen  has 
the  same  meaning  as  the 
following  more  technical 
one;  namely,  burning  hy- 
drogen affords  thirty-four 
thousand  four  hundred  and 
sixty-two  thermal  units. 
Now  carbon,  a  fuel  which 
nature  has  provided,  ami 
which  is  certainly  admira- 
bly fitted  to 'be  man's  chief 
combustible,  yields  but 
eight  thousand  and  eighty 
thermal  units  of  the  kind 
just  referred  to,  and  for 
purposes  of  comparison  it  may  be  added  that  sulphur  yield? 
but  two  thousand  two  hundred  and  sixty  thermal  units. 


FIG  8. — A  glass  tube  held  over  a  hydrogen 
flame,  for  the  purpose  of  developing  a  mus- 
ical note. 


Hydrogen   Cannot   Supply   the   Uses   of  Atmos- 
pheric Air. 

Notwithstanding  the  remarkable  evidences  of  chemical 
affinity  suggested  by  what  has  just  been  said,  hydrogen  can 
in  no  sense  act  as  a  substitute  for  the  atmospheric  air.  Thus, 
it  does  not  support  animal  life  nor  will  it  sustain  the  com- 
bustion of  a  caudle.  A  living  animal  immersed  in  a  room 
full  of  hydrogen  would  be  drowned  in  it;  a  burning  candle 
carried  into  such  a  chamber  would  be  extinguished  as  if 
dipped  in  water.  In  fact  the  comparison  with  drowning  is 
very  proper,  for  in  drowning  a  living  animal  the  water  does 
5 


66 


CHEMISTRY. 


not  chemically  injure  the  organism;  the  hydrogen  and  the 
water,  in  the  cases  supposed,  have  similar  action  in  prevent- 
ing  both  the  animal  and  the  taper  from  securing  their  supply 
of  oxygen. 

Uses  to  Which  Hydrogen  May  be  Put. 

Hydrogen  as  the  elementary  gas  finds  but  few  applications 
in  the  arts.  It  is  true  that  from  what  has  been  said  it  ap- 
pears as  if  its  wonderful  calorific  power  might  be  utilized  in 
some  of  the  arts  where  high  temperatures  are  requisite.  But 


FIG.  9.— Disposition  of  apparatus  for  the  production  of  water,  by  combustion  of  dry 
hydrogen  in  air. 

the  cost  and  difficulties  attending  its  preparation,  the  liabil- 
ity to  loss  during  its  storage,  and  the  danger  from  explosion 
while  in  actual  use,  these  and  other  circumstances  have  led 
even  the  skilled  artisan  to  content  himself  in  most  cases  with 
other,  though  inferior,  materials. 

But  if  the  reader  has  attentively  followed  the  introductory 
chapters  of  this  work  he  must  have  perceived  that  hydrogen 
is  made  of  great  service  in  many  of  the  measurements  em- 
ployed by  the  chemist.  It  has  been  noted  that  it  is  used  as 


HYDROGEN.  6? 


the  standard  of  equivalence  or  atom-fixing  power.  It  has 
been  spoken  of  as  the  standard  of  atomic  weif/ht,  and  from 
what  has  appeared  in  the  remarks  upon  its  lightness  it  seems 
that  it  has  been  properly  adopted  as  the  standard  of  density 
j'or  gases. 


READING   REFERENCES. 
Cavendish,  Henry. 

Brougham,  H.— Lives  of  Men  of  Letters  and  Science,  etc.     p.  420. 
Timbs,  J. — English  Eccentrics,  etc.     p.  132. 
Wilson,  George. — Life  of  Cavendish.     London.     1851. 
Clerk-  Maxwell  J. — Electrical  Researches  of  Hon.  H.  Cavendish. 
Cambridge. 

Black,  Joseph. 

Brougham,  H. — Lives  of  Men  of  Letters  and  Science,  etc.    London. 
1845.     p.  324. 

Diffusion  of  Gases. 

Graham,  T. — Elements  of  Chemistry.    2  v.    London.    1850.    i,  84. 
Jour,  of  Chem.  Soc.  of  London,     xvii.  334. 

Occlusion  of  Hydrogen  by  Palladium. 

Graham,  T. — Jour,  of  Chem.  Soc.  of  London,     xxii,  419. 


C8  CHEMISTRY. 


X. 

BALLOONS. 

]HE  remarkable  lightness  of  hydrogen  early  sug- 
gested the  fitness  of  that  gas  for  the  inflation  of 
balloons.  From  the  earliest  ages  men  have  desired 
to  navigate  the  air.  The  drudgery  of  land  travel- 
ing over  hills  and  mountains,  over  marshes  and  streams, 
through  jungles  and  forests,  has  led  men  to  prefer  voyaging 
even  by  sea.  Thus  the  people  of  the  United  States  crossed 
the  stormy  Atlantic  in  large  numbers  long  before  they  trav- 
ersed the  wilds  of  the  American  continent  to  the  Pacific 
coast ;  and  the  early  voyagers  from  New  York  to  the  Golden 
Gate  of  San  Francisco  preferred  the  water  way,  though  it  led 
them  through  an  enormous  distance  and  around  the  perilous 
Cape  Horn,  rather  than  undertake  the  shorter  course  over 
the  Rocky  Mountains.  Even  at  a  later  date,  the  sea  voyage 
to  Panama,  and  across  the  Isthmus,  and  again  by  water  way 
to  San  Francisco  was  the  ordinary  course,  until  Pacific  rail- 
roads created  a  land  pathway  from  one  side  of  the  continent 
to  the  other.  So  men,  envying  the  bird  in  its  flight  through 
the  mobile  air,  have  desired  yet  more  to  conquer  its  smooth 
courses,  just  as  their  keels  have  found  a  sliding  pathway  in 
the  watery  main.  But  no  truly  successful  air-voyaging  was 
possible  until  about  one  hundred  years  ago. 

Invention  of  the  Balloon. 

In  the  year  1783  two  brothers,  named  Stephen  MontgolHer 
and  Joseph  Montgolfier,' succeeded  in  sending  up  into  the 
atmosphere  the  first  air-ship  worthy  of  the  name.  They  lived 
in  France,  at  a  little  town  named  Annonay,  situated  about 
forty  miles  south  of  Lyons,  and  at  the  junction  of  two  small 
streams  whose  clear  waters  flow  into  the  Rhone.  Here  the 
brothers  carried  on  with  increasing  skill  and  success  the  manu- 


BALLOONS. 


69 


facture  of  paper,  a  business  which  their  father  had  conducted 
there  before  them,  and  which  in  fact  is  carried  on  by  their 
descendants  of  the  same  name  even  at  the  present  day.  The 
brothersj  Stephen  and  Joseph,  were  skillful  mechanics,  and 
one  of  them,  it  is  said,  had  studied  Dr.  Priestley's  work  on 
"  Different  Kinds  of  Air."  This  seems  to  have  led  him  to 


•I 


FIG.  10.— One  of  the  balloons  of  the  Montgolfler  brothers. 

the  idea  of  nerial  navigation.  However  that  may  be,  it  is  a 
matter  of  history  that  on  the  5th  of  June,  1783,  the  two 
brothers  sent  up  from  Annonay  a  balloon  about  thirty-five 
feet  in  diameter.  Naturally  it  was  marie  of  paper,  though 
lined  with  linen.  The  ascensional  power  of  this  balloon  was 
due  to  a  proportional  lightening  of  the  air  within  it  by  the 
influence  of  heat.  The  heat  was  produced  by  the  combustion 
of  a  large  quantity  of  chopped  straw,  and  also  from  burning 
wool  previously  saturated  with  a  little  alcohol.  Probably 


70  CHEMISTRY. 


the  Montgolfier  brothers  did  not  then  fully  know  why  their 
balloon  ascended  :  they  appear  to  have  thought  that  it  arose 
because  of  the  volumes  of  smoke  that  filled  it.  It  is  hardly 
probable  that  either  Stephen  or  Joseph  Montgolfier  thought 
at  that  time  of  using  hydrogen  for  their  air-ship,  notwith- 
standing its  extraordinary  lightness  had  been  a  matter  of 
public  scientific  knowledge  for  six  or  seven  years.  This  mny 
seem  the  more  strange  in  view  of  the  admitted  fact  that  as 
early  as  1767  Dr.  Black,  of  Edinburgh,  had  publicly  demon- 
strated that  a  suitable  vessel  filled  with  hydrogen  would 
ascend  in  the  atmosphere  as  cork  does  in  water.  Of  course 
they  did  not  think  of  employing  illuminating  gas,  because 
that  substance  was  not  then  in  public  use. 

The  First  Balloon  Ascension  in  Paris. 

The  news  of  the  wonderful  and  successful  experiment  at 
Annonay  was  quickly  sent  to  Paris,  where  it  produced  a 
profound  sensation.  The  interest  extended  from  scientific 
men  to  the  royal  family  and  the  court,  and  indeed  to  the 
entire  population  of  the  capital.  For  the  French  people — 
perhaps  even  more  than  other  nations  of  Europe — seern  to 
have  been  particularly  interested  at  this  time  in  the  study 
of  chemical  and  physical  science.  The  king  instantly  issued 
a  summons  for  the  Montgolfiers  to  come  to  Paris.  But  the 
Parisians  could  not  even  await  their  arrival.  The  scientists 
of  the  capital,  though  but  partially  informed  as  to  the  char- 
acter of  the  experiments  performed  at  Annonay,  at  once  set 
to  work.  They  decided  upon  hydrogen  gas  as  probably  the 
best  fitted  for  their  purposes.  Whereupon  they  filled  a  glob- 
ular balloon  with  this  gas,  nnd  prepared  to  try  it  in  public 
upon  the  Champ- de-Mars.  It  is  said  "that  three  hundred 
thousand  people — that  is,  nearly  half  the  population  of  Paris 
— gathered  together,  crowding  every  adjacent  avenue,  to 
witness  the  unparalleled  undertaking.  The  liberation  of  the 
aerial  messenger  was  announced  to  the  public  by  a  salvo  of 
artillery.  The  balloon  immediately  shot  upward  and,  pierc- 


BALLOONS. 


71 


ing  the  clouds,  was  soon  lost  to  view.  When  afterward  it 
slowly  descended  it  reached  the  ground  some  fifteen  miles 
from  Paris.  Here  a  troop  of  peasants  who  detected  the 
strange  apparition  were  at  first  struck  with  alarm,  but 
quickly  rallied,  attacked  the  monster  and,  of  course,  soon  re- 
duced it  to  shreds.  The  whole  chain  of  circumstances 
created  so  much  excitement  that  the  Government  thought 
proper  to  issue  a  proclamation  upon  the  subject.  A  copy  of 
this  interesting  document  is  here  presented  in  its  original 
form.  Perhaps  some  readers  will  find  the  accompanying 
translation  acceptable : 

French  Proclamation  Respecting  Balloons. 


Avertissement  au  people  sur  I'en- 
levement  des  baltons  ou  globes  en 


On  a  fait  une  decouverte  dont 
le  gouvernement  a  juge  convena- 
ble  de  donner  connaissance,  afin 
de  prevenir  les  terreurs  qu'elle 
pourrait  occasioner  parmi  le  peu- 
ple.  En  calculant  la  difference 
de  pesanteur  entre  1'air  appele 
inflammable  et  1'air  de  notre  at- 
mosphere, on  a  trouve  qn'un  bal- 
lon rempli  de  cet  air  inflamma- 
ble devait  s'elever  de  lui-meme 
dans  le  ciel  jusqu'  au  moment  oh 
les  deux  airs  seraient  en  equili- 
bre,  ce  qui  ne  peut  etre  qu'  a  une 
tres  grnnde  hauteur.  La  prem- 
iere experience  a  ete  faite  a  An- 
nonay,  en  Vivarais,  par  les  sieurs 
Montgolfier,  iriventeurs.  Une 
ji'lobe  de  toile  et  de  papier  de 
cent  cinq  pieds  de  circonference, 
rempli  d'air  inflammable,  s'eleva 
lui-meme  a  une  hauteur  qu'  on  n' 
a  pu  calculer.  La  meme  expe- 
rience vient  d'etre  renouvelee  a 
Paris,  le  27  aout  a  cinq  heurs  du 


Notice   to    the  public    relative    to   the 
ascension  of  balloons  or  globes  into  the 


A  'discovery  lias  been  made  to  which 
the  Government  considrs  it  adviseable 
to  call  public  attention,  with  a  view 
of  preventing  alarms  which  it  other- 
wise might  occasion  among  the  people. 
Upon  calculating  the  difference  of 
weight  between  the  gas  called  in- 


flammable   air     and 
atmosphere    it    has 


the    air     of    our 
been     discovered 


that  a  balloon  filled  with  this  in- 
flammable air  ought  to  rise  of  itself 
to  a  height  in  the  sky  such  that  the 
air  within  and  that  without  will  be 
in  equilibrium,  a  condition  which  will 
not  be  reached  except  at  a  very  great 
elevation.  The  first  experiment  of  this 
sort  has  been  made  at  Annonay,  in 
Vivarais,  by  the  Messrs.  Montgolfier, 
the  inventors.  A  globe  of  cloth  and 
paper  one  hundred  and  five  feet  in 
circumference  and  filled  with  inflam- 
mable air  rose  of  itself  to  a  height 
which  the  observer  could  not  calcu- 
late. The  same  experiment  has  just 
been  repeated  at  Paris  on  the  27th 


CHEMISTRY. 


soir,  en  presence  d'un  nombre  in- 
fini  de  personnes.  Un  globe  de 
taffetas  enduit  de  gomme  elas- 
tique,  de  trente-six  pieds  de  tour, 
s'est  eleve  du  Champ  de-Mars 
jusque  dans  les  nues,  oh  on  1'a 
perdu  de  vue.  On  se  propose  de 
repeter  cette  experience  avec  des 
globes  beaucoup  plus  gros. 

Chacun  de  ceux  qui  decouv- 
riront  dans  le  ciel  de  pareils 
globes,  qui  presentent  1'aspect  de 
la  lune  obscurcie,  doit  done  etre 
preveuir  que,  loin  d'etre  uu  phe- 
nomene  effrayant,  ce  n'est  qu'une 
machine  tou jours  composee  de 
taffetas  ou  de  toile  legere  re- 
couverte  de  papier,  qui  ne  pent 
causer  aucuu  mal,  et  dont  il  est 
a  presurner  qu'on  fera  quelque 
jour  des  applications  utiles  aux 
besoins  de  la  societe. 

Lu  et  approve, 
ce  3  septembre,  1783. 

DF  SAUVIGNY. 


of  August  at  5  o'clock  in  the  afternoon, 
in  presence  of  a  vast  number  of  per- 
sons. A  sphere  of  taffeta  coated  with 
gum  elastic,  thirty-six  feet  in  circum- 
ference, ascended  from  the  Champ- 
de-Mara  even  to  the  clouds,  in  which 
it  became  lost  to  sight.  It  is  contem- 
plated repeating  this  experiment  with 
very  much  larger  globes. 

Any  one  who  discovers  in  the 
sky  globes  of  this  sort,  which  present 
the  appearance  of  the  moon  when 
slightly  obscured,  may  therefore  be 
warned  that,  far  from  being  an 
alarming  phenomenon,  this  is  nothing 
but  a  machine  always  constructed 
of  taffeta  or  of  light  cloth  covered 
with  paper,  which  cannot  do  any 
injury,  and  which  it  is  thought 
will  assume  at  some  future  time 
a  form,  that  will  prove  useful  to  the 
public. 

Read  and  approved, 
September  3,  1783. 

DE  SAUVIGNY. 


The  enthusiasm  created  by  the  original  experiment  of  the 
Montgolfier  brothers  led  soon  after  to  the  election  of  both 
of  them  to  the  Academy  of  Sciences.  Moreover  their  inven- 
tion was  not  allowed  to  rest  long  in  its  original  form. 

As  early  as  November  of  the  same  year,  1783,  two  French 
gentlemen  had  the  courage  to  risk  their  lives  in  an  ascension 
from  Paris  in  a  balloon  of  the  Montgolfier  construction. 
They  floated  freely  away  and  made  their  landing  in  safety. 
One  of  them,  however,  De  Rozier  by  name,  on  a  later  occa- 
sion attempted  to  cross  the  Channel  in  a  double  balloon — one 
part  containing  hydrogen,  the  other  heated  air  in  the  Mont- 
golfier style — but  at  a  great  altitude  the  hydrogen  balloon 
took  fire  from  the  other,  and  De  Rozier  and  his  companion 
were  dashed  to  pieces  on  the  rocks  of  the  French  coast. 
Since  that  early  rash  attempt  thousands  of  interesting  and 


8? 

S 


:   ••   .-    i    «  :    ?  • 

fi  !     S 
S 1 1 1  J«1J 


FIG.  11.— Gay-Lussac  and  Biot  making  their  balloon  ascension  for  scientific  observations  In 

(73) 


74  CBEMIST&Y. 


safe  balloon  ascensions  have  been  made,  and  increased 
knowledge  of  the  scientific  principles  has  largely  contributed 
to  the  pleasure  and  comfort  of  the  aeronaut.  Yet  the  con- 
trivance has  been  in  most  cases  little  more  than  a  scientific  toy. 

The  atmospheric  air  has  thus  far  baffled  the  inventive 
power  of  man  to  such  an  extent  that  the  balloon  as  a  me- 
chanical contrivance  has  been  subjected  to  but  few  decided 
improvements  since  the  Montgolfiers'  first  experiments,  and 
ascensions  have  afforded  comparatively  meager  scientific  or 
other  results.  Indeed  the  most  of  them  have  been  conducted 
for  personal  gratification  or  popular  entertainment. 

Of  course  there  are  marked  exceptions.  Thus  on  the  24th 
of  August,  1804,  two  of  the  youngest  but  most  distinguished 
of  French  physicists,  Messrs.  Gay-Lussac  and  Biot,  made  an 
important  ascension.  Their  voyage  was  upon  the  suggestion 
of  the  French  Academy  of  Sciences,  and  they  were  well 
equipped  with  apparatus  for  making  observations.  Their 
results,  particularly  in  magnetism,  showed  the  same  laws 
prevailing  in  the  higher  air  as  upon  the  earth.  But  as  there 
were  afterward  expressed  some  doubts  as  to  the  accuracy  of 
these  observations,  Gay-Lussac  made  a  later  and  higher 
ascent  alone.  On  the  16th  of  September  he  attained  an  alti- 
tude of  twenty-three  thousand  feet,  the  greatest  reached  up 
to  that  date.  His  experiments  on  this  occasion  verified 
those  made  before.  Of  particular  interest  was  his  test  of 
the  composition  of  the  atmosphere.  The  bottle  of  air  col- 
lected at  this  great  height  was  found  upon  analysis  to  pos- 
sess the  same  proportional  amounts  of  oxygen  and  nitrogen 
as  that  collected  at  the  surface  of  the  earth.* 


*  Of  Gay-Lussac  and  this  ascension  there  is  told  a  pretty  tale,  which  I  will  not  mar 
by  making  a  translation  : 

"  Parvenu  a  la  hauteur  de  7000  metres, il  voulut,  dit-il,  essayer  de  monter  plus  haut. 
et  se  de"barrassa  de  tous  les  objets  dont  il  pouvait  rigoureusement  se  passer.  Au  nom- 
ber  de  ces  objets  flgurait  une  chaise  en  bois  blanc,  que  le  hasard  fit  tomber  sur  un 
buisson,  tout  pres  d'une  jeune  fllle  qui  gardait  les  moutons.  Quel  ne  fut  pas  re"tonne- 
ment  de  la  bergere! — Comme  eut  dit  Florian. — Le  ciel  e"tait  pur,  le  ballon  invisible. — 
Que  penser  de  la  chaise,  si  ce  n'est  qu'elle  provenait  du  paradis  ?— On  ne  pouvait  ob- 
jecter  a  cette  conjecture  que  la  grpssierete  du  travail :  les  ouvriers,  disaient  les  incred- 
ules,  ne  pouvalent  la-haut  etre  si  inhabiles.  La  dispute  en  etat  la,  lorsque  les  jour- 
naux,  en  publiant  toutes  les  particuliarites  du  voyage  de  Gay-Lussac,  y  mirent  fln,  en 
rangeant  parmi  les  effets  naturels  ce  qui  jusqu'  alors  avait  parut  un  miracle." — 
Arago;  Eloge  de  Gay-Lussac. 


BALLOONS.  75 


The  height  of  this  ascent  has  since  been  surpassed  by 
Messrs.  Glaisher  and  Cox  well,  of  England,  who  on  Septem- 
ber 5,  1862,  attained  an  altitude  of  about  thirty-seven  thou- 
sand feet. 

Recent  Use  of  Balloons. 

Hydrogen  is  the  lightest  substance  known,  and  this  con- 
sideration tends  to  make  it  a  particularly  favorable  one  for 
the  inflation  of  balloons.  But  we  have  seen  that  it  was  not 
until  after  the  Montgolh'er  experiments  that  hydrogen  came 
into  considerable  use  for  this  purpose.  Hydrogen  is  still 
occasionally  prepared  for  purposes  of  this  sort.  It  is  then 
produced  by  the  action  of  sulphuric  acid  upon  zinc.  The 
equation,  already  given,  explaining  this  action  is  as  follows: 

Zn  -f  H2SO4  ZnSO4  +          H2 

One  atom  of  One  molecule  of  One  molecule  of  One  molecule  of 

Zinc,  Sulphuric  acid,  Zinc  sulphate,  Hydrogen, 

65  98  161  2 

parts  by  weight.  parts  by  weight.  parts  by  weight.  parts  by  weight. 


163  163 

In  case  zinc  is  not  at  hand,  iron-turnings  have  been  made 
to  answer  the  same  purpose;  and  the  chemical  change  in  this 
event  is  represented  by  an  equation  of  very  similar  form: 


Fe 

+          H2S04 

=           FeSO4 

h          H2 

One  atom  of 

One  molecule  of 

One  molecule  of 

One  molecule  of 

Iron, 

Sulphuric  acid, 

Ferrous  sulphate, 

Hydrogen, 

56 

98 

152 

2 

parts  by  weight. 

parts  by  weight. 

parts  by  weight. 

parts  '••   w  ight. 

154  154 

Both  of  these  methods  of  producing  hydrogen  are  still 
somewhat  used  where  balloons  have  to  be  inflated  at  points 
distant  from  a  city  gas  supply.  But  ihe  manufacture  of  illu- 
minating gas  is  now  so  general,  even  in  small  towns,  that  this 
substance  is  oftener  used  at  the  present  day.  The  superior 
convenience  with  which  it  may  be  obtained  makes  it  pre- 
ferred to  hydrogen,  notwithstanding  the  greater  ascensional 
power  of  the  latter  substance. 


CHEMISTRY. 


FIG.  12.— Carrier  pigeon  having  attached  to  his  tail  a  quill  containing  microscopic 
photographs  of  dispatches  to  be  sent  into  Paris  during  the  siege. 


FIG.  13.— The  tube  of  quill  containing  messages  as  attached  to  the  tail-feathers  of 
a  carrier  pigeons. 


FIG.  14.— Owner's  name  on  the  wing  of  si  pigeon. 

Balloons  have  been  used  somewhat  in  recent  wars.  Thus 
they  were  found  of  considerable  service  during  the  siege  of 
Paris,  particularly  from  September  23,  1870,  to  January  28, 


BALLOONS. 


1871.     During  these  last  four  months  of  that  siege  sixty-two 

balloons  left  the  city,  and  they  carried  out  above  two  mill- 

ion letters  and   a   great  many  homing   pigeons.     Some  of 

the    birds    returned,    escaping    the 

Prussian     sharp  -  shooters,    and 

brought  with  them  letters  and  dis- 

patches, printed  upon  the  thinnest 

of  paper,    in   the   form    of   micro- 

scopic  photographs.     The  balloons 

also  took  out  of  Paris  during  the 

siege  two  especially  notable  passen- 

gers, the  one,  Leon  Gambetta,  head 

of  the  provisional  government,  who 

left  the  city  for  the  purpose  of  con- 

ducting the  public  business  in  the 

provinces  ;      the     other,     Professor 

Janssen,  who   had   the   courage   to 

venture  out  in  the  darkness  of  early     FIG.  15.—  Fac-simiie  of  a  micro- 

morning,  so  as  to  escape  the  rifles  of  ^ndispLae^rf  and 

the  beleaguring   forces.     His   voy- 

age  was  for  the  purpose  of  reaching 

the  station  in  Algeria  from  which  he 

was  to  observe  the  total  eclipse  of 

the  sun,   to  occur  a  few  weeks   later,  December  22,  1870. 

Readers  who  are  interested   in  the  use  of  balloons  during 

this  memorable  siege  will  find  an  excellent  account  in  Mr. 

Glaisher's  book,  Travels  in  the  Air.     It  contains  a  descrip- 

tion of  the  manufacture  of  air-ships  in  Paris,  together  with 

a  list  of  the  passengers  and  an   account  of  the  freight  of 

those  leaving  the  city  when  other  means  of  communication 

with  the  outside  world  were  cut  off. 


SSd 

^  appearance 


The  Centenary  of  Ballooning. 

It  is  worthy  of  note  that  in  August,  1883,  the  centenary 
of  the  experiment  of  the  Montgolfier  brothers  was  celebrated 
by  their  descendants  and  others  at  Annonay  by  a  modern 


78  CHEMISTRY. 


balloon  ascension  and  other  fetes.  These  included  the  dedi- 
cation of  a  monument  to  the  two  inventors,  the  monument 
to  be  surmounted  by  a  group  in  bronze  representing  the  two 
brothers  inflating  their  first  balloon. 


READING  REFERENCES. 
Balloons,  Their  Early  History. 

Figuier,  L. — Les  Aerostats  ct  les  Aeronautes.  Revue  des  Deux 
Mondes.  Oct.  1,  1850.  p.  193. 

[This  interesting  article  will  well  repay  the  reader.] 

Blerzy,  H. — La  Navigation  Aerienne.  Kevue  des  Deux  Mondes. 
Nov.,  1863.  p.  279. 

[Claim  is  here  made,  in  a  general  way,  that  the  original  invention  of  the 
balloon  was  made  at  the  close  of  the  seventeenth  century  by  a  Portuguese  named 
Gusmao.] 

Balloons,  Their  Recent  Uses. 

Glaisher,  James,  and  others. — Travels  in  tlie  Air.     London.     1871. 
Hofmann,  A.  W.—  Chem.  News,     xxxii,  231,  241,  255,  265. 

Balloons,  Centenary  of  Their  Invention. 

London  Graphic.     August  25,  1883. 

Balloons,  Popular  Account  of. 

Harper's  Magazine,     ii,  168,  323;  xxxix,  145. 
Scribner's  Monthly,     i.  385. 
Gay-Lussac. 

Arago,  D.  F.  J.— (Euvres  Completes.     Paris.     1854-59.     iii, 
[The  Boston  Athenaeum  library  has  this  work.] 


CHLORINE.  79 


XI. 

CHLORINE. 

[HLORINE  has  extraordinary  bleaching  powers, 
and  in  that  form  of  combination  known  as 
bleaching-powder  it  is  extensively  used  for  the 
whitening  of  cotton  and  linen  goods.  Thus  chlo- 
rine acquires  great  commercial  importance. 

Chlorine  is  contained  in  common  salt,  whether  it  is  in 
the  brine  of  the  ocean  or  of  mineral  springs,  or  whether  it 
occurs  as  a  solid  rock.  As  a  constituent  of  salt,  therefore,  it 
becomes  an  important  article  of  human  food. 

Salt  is  very  widely  distributed.  At  Wieliczka,  in  Austria, 
mines  of  solid  salt  have  been  worked  for  hundreds  of  years. 
So  also  at  Cardona,  in  Spain,  are  what  may  be  called  quar- 
ries of  this  valuable  mineral  ;  while  Cheshire,  in  England, 
furnishes  immense  solid  deposits  from  which  salt  is  obtained 
to  supply  the  enormous  industrial  establishments  using  this 
substance  for  the  production  of  chlorine  and  of  compounds 
of  sodium. 

Chlorine  was  first  recognized  as  a  distinct  substance  by 
a  European  chemist,  Carl  Wilhelm  Scheele.  He  was  known 
to  his  neighbors  as  little  more  than  a  humble  apothecary, 
even  when  his  chemical  experiments  were  exciting  an  in- 
terest all  over  Europe.  Scheele  was  born  at  Stralsund,  a 
seaport  town  of  Pomerania,  situated  on  the  little  strait 
which  leaves  the  island  of  Rtigen  in  the  Baltic  Sea.  He 
spent  the  principal  portion  of  his  life  in  Sweden,  and  on 
this  account  is  often  referred  to  as  a  Swedish  chemist. 
Though  living  in  great  obscurity  and  dying  at  an  early  age, 
he  yet  made  many  discoveries  in  chemistry  which  have 
rendered  his  name,  otherwise  almost  unknown,  one  of  the 
most  brilliant  in  the  annals  of  this  science. 

It  is  related  that  the  King  of  Sweden,  Gustavus  III.,  while 


FIG.  16.-Sir  Humphry  Davy,  Bart.    Bora  In  Penzance,  England,  Dec.  17,  1778  ;  died  in 


yO  years  old,  occupied,  in  the  opinion  of  all  those  who  could 
Judge  of  such  labors,  the  first  rank  among  the  chemists  of  this  or  any  other  age." 

(80) 


CHLORINE.  81 


on  a  journey  outside  of  his  own  dominions,  heard  so  much 
of  the  fame  of  this  chemist,  unknown  to  him  before,  that  he 
regretted  having  previously  done  nothing  for  him.  He 
therefore  commanded  that  Scheele  receive  the  honor  of 
being  created  chevalier.  "Scheele?"  "Scheele?"  said  the 
minister  charged  with  this  duty.  "  This  is  very  singular  ; 
what  in  the  world  has  Scheele  done  ?  "  The  order  was  per- 
emptory, however,  and  a  Scheele  was  knighted.  But,  as  the 
reader  may  perhaps  divine,  the  honor  designed  for  the 
acute  discoverer  fell  upon  another  Scheele — not  upon  that 
Scheele  unknown  at  court  but  illustrious  among  the  scien- 
tists of  Europe. 

It  was  this  obscure  apothecary,  then,  who  added  to  the 
list  of  his  other  investigations  a  study  of  the  properties  of 
what  was  ordinarily  considered  a  dull  and  uninteresting  earthy 
substance  called  black  magnesia.  This  study  was  repaid  by 
the  revelation  of  no  less  than  four  hitherto  unknown  sub- 
stances: oxygen,  barium,  manganese,  and  finally  chlorine. 
Scheele  obtained  the  chlorine  in  the  year  1774  exactly  as  it 
is  done  at  the  present  day ;  namely,  by  bringing  together 
the  two  substances  now  called  hydrochloric  acid  and  black 
oxide  of  manganese,  but  then  known  as  muriatic  acid  and 
black  magnesia. 

Scheele  believed,  and  other  celebrated  chemists  concurred 
in  the  opinion,  that  the  greenish  gas  that  he  discovered  was 
a  compound  substance.  It  was  not  until  thirty-six  years 
later — that  is,  1810,  that  the  distinguished  English  chemist, 
Sir  Humphry  Davy,  demonstrated  that  this  gas  is  not  a 
compound,  but  is  in  fact  a  simple  elementary  substance;  and 
it  was  he  who  gave  to  it  the  name  chlorine,  a  name  derived 
from  a  Greek  word  (^Awpo^,  chloros,  meaning  light  green), 
conveying  an  obvious  and  convenient  reminder  of  one  strik- 
ing property  of  the  thing  referred  to. 

How  Chlorine  is  Obtained. 

The  preparation  of  chlorine  is  a  very  simple  matter.  It 
may  be  accomplished  by  placing  some  powdered  black  oxide 


82  CHEMISTRY. 


of  manganese,  an  abundant  mineral  substance,  in  any  deep 
glass  vessel,  and  then  adding  to  it  four  or  five  times  its 
weight  of  hydrochloric  acid.  Any  one  who  performs  the 
experiment  will  soon  perceive  the  greenish  gas  rising  higher 
and  higher  in  the  vessel,  and  will  soon  discover  its  choking 
and  corosive  odor.  Moreover,  the  chlorine  gas,  which  is 
two  and  a  half  times  as  heavy  as  air,  accumulates  within  the 
flask  and  stays  there  some  time.  This  is  the  process  which 
has  already  been  referred  to  as  that  which  first  revealed  the 
gas  to  Scheele,  and  this  process,  with  but  slight  modifica- 
tion, is  that  which  to-day  furnishes  the  enormous  quantities 
of  chlorine  demanded  by  modern  industries. 

The  Characteristics  of  Chlorine. 

The  three  most  striking  properties  of  chlorine  are  its 
noticeable  weight — greater  than  that  of  the  air — its  greenish 
color,  and  its  exceedingly  irritating  odor.  Its  influence  on 
the  animal  organism  is  very  violent  :  more  than  one  exam- 
ple can  be  produced  of  fatal  results  following  the  inhalation 
of  too  large  quantities  of  the  gas.  Thus  Pelletier,  a  French 
chemist,  died  at  Bayonne  from  the  effects  of  inhaling  a  con- 
siderable quantity  of  chlorine,  and  Roe,  a  young  Irish 
chemist  of  Dublin,  lost  his  life  from  the  same  cause,  while 
studying  the  properties  of  this  gas. 

Chlorine,  as  a  chemical  agent,  manifests  its  activities  in 
connection  with  two  principal  properties  ;  namely,  its  affin- 
ity for  hydrogen  and  its  affinity  for  the  metals.  By  this 
statement  it  is  meant  that  chlorine  manifests  a  strong  tend- 
ency to  combine  with  hydrogen  and  to  combine  witli 
metals  whenever  these  substances  arc  accessible  to  it. 

When  it  combines  with  hydrogen  it  ,  orms  the  important 
compound  designated  by  the  formula  lit.^  and  called  by 
the  chemist  hydrochloric  acid,  but  known  in  commerce  as 
muriatic  acid. 

When  chlorine  combines  with  the  metals  it  forms  chlo- 
rides of  them.  Thus  with  the  metal  sodium  it  forms  the 
compound  designated  by  the  formula  NaCl  and  called  by 


CHLORINE.  83 


the  chemist  indifferently  sodic  chloride  or  chloride  of 
sodium;  these  will  be  recognized  as  the  chemical  names  for 
the  important  and  well-known  substance,  common  salt. 

Chlorine  and  Hydrogen  Combine. 

Chlorine  and  hydrogen  have  a  very  strong  tendency  to 
combine  with  each  other.  They  manifest  this  tendency  in  a 
variety  of  ways.  Thus,  if  the  two  gases  are  prepared  in  a 
dark  room,  they  may  be  there  safely  mixed  together  in  a 
glass  vessel;  but  if  the  sunlight  be  allowed  to  enter  and  fall 
upon  the  vessel  there  is  danger  of  its  being  shattered  by 
the  explosive  violence  with  which  the  hydrogen  and  chlorine 
immediately  unite.  As  a  result  of  this  combination  hydro- 
chloric acid  is  produced. 

The  chemical  change  is  represented  by  the  following  equa- 
tion : 

H2  -f  C13  2HC1 

One  molecule  of  One  molecule  of  Two  molecules  of 

Hydrogen,  Chlorine,  Hydrochloric  acid, 

2  71  73 

parts  by  weight.  parts  by  weight.  parts  by  weight. 


73  73 

Again,  when  chlorine  is  brought  in  contact  with  vegetable 
or  animal  substances  containing  hydrogen,  it  proceeds  to 
withdraw  that  hydrogen  for  its  own  benefit,  even  though 
these  vegetable  and  animal  compounds  are  thereby  destroyed. 

Although  this  operation,  as  well  as  the  foregoing  one,  pro- 
duces hydrochloric  acid,  yet  neither  method  is  suitable  for  a 
determinate  preparation  of  that  substance.  It  is  usually  better 
to  prepare  hydrochloric  acid  in  another  way.  Thus  it  is  easily 
produced  by  the  ac^'jun  of  sulphuric  acid  upon  common  salt. 

Experimental  Preparation  of  Hydrochloric  Acid. 

Any  one  who  will  take  a  little  trouble  may  prepare  hydro- 
chloric acid  in  the  way  indicated. 

The  experiment  should  be  conducted  as  follows : 

Place  a  small  amount  of  common  salt  (Na  Cl)  in  a  small 


84 


CHEMISTRY. 


retort;  to  it  add  enough  concentrated  sulphuric  acid  to 
make  a  thin  paste;  connect  the  neck  of  the  retort  with  a 
clean  test-tube  containing  a  few  drops  of  water.  Now 
gently  heat  the  retort ;  hydrochloric  acid  will  be  formed  and 
will  distill  from  the  retort  and  condense  in  the  receiver. 


FIG.  17.— Section  of  furnace  used  for  manufacture  of  hydrochloric  acid.  Common 
salt  and  sulphuric  acid  are  placed  in  the  large  retort  A  ;  upon  heating,  hydrochloric 
acid  passes  into  the  receivers  C,  C,  C. 

The  chemical  change  is  represented  by  the  following  equa- 
tion : 

NaCl      +        H2SO4        =          HC1  -f        HNaSCX 

One  molecule  of         One  molecule  of  One  molecule  of  One  molecule  of 

Sodic  chloride,     Sulphuric  acid,    Hydrochloric  acid.     Hydro-sodic  sulphate, 

58£  98  36£  120 

parts  by  weight.          parts  by  weight.  parts  by  weight.  parts  by  weight. 


The  product  of  the  foregoing  experiment  may  be  tested  in 
three  ways,  and  so  shown  to  be  in  fact  hydrochloric  acid. 


CHLORINE.  85 


First:  Take  a  minute  drop  on  a  glass  rod  and  apply  it  to 
the  tongue  and  observe  the  sour  or  acid  taste. 

Second:  Take  a  drop  on  a  glass  rod  and  touch  it  upon 
blue  litmus-paper.  It  should  turn  the  paper  red. 

Third:  Pour  a  few  drops  of  the  liquid  into  a  solution  of 
argentic  nitrate  (that  is,  nitrate  of  silver)  in  a  test  tube  or 
other  convenient  vessel:  a  white  precipitate  of  argentic 
chloride  will  be  formed. 

The  method  of  producing  hydrochloric  acid  just  described 
and  illustrated  is  followed  in  the  manufacture  of  the  sub- 
stance for  general  chemical  purposes.  It  is  also  employed 
for  the  production  of  the  enormous  quantities  of  it  inci- 
dentally used  in  the  manufacture  of  bleaching-powder, 

Experiments  with  Common  Salt. 

Chlorine  has  already  been  shown  to  combine  with  the 
metal  silver,  producing  the  compound  designated  by  the 
formula  Ag  Cl,  and  called  argentic  chloride  and  also  chloride 
of  silver.  This  substance  may  also  be  prepared  very  easily 
somewhat  as  follows  : 

Make  a  solution  of  nitrate  of  silver.  Prepare  it  either  by 
dissolving  in  water  the  crystals  sold  by  apothecaries,  or  by 
dissolving  a  small  piece  of  silver  in  nitric  acid.  Then  make 
a  second  clear  solution,  by  dissolving  common  salt  in  ordi- 
nary water.  Add  the  salt  solution  cautiously,  drop  by  drop 
to  the  silver  solution.  There  immediately  appear  thick 
masses  of  white  flakes  which  sooner  or  later  fall  to  the  bot- 
tom of  the  vessel.  These  flakes  consist  of  the  argentic  chlo- 
ride (Ag  Cl),  also  called  chloride  of  silver,  already  referred  to. 

The  chemical  change  is  represented  by  the  following  equa- 
tion : 

AgNO3          H-        NaCl  AgCl          +         NaNO3 

One  molecule  of  One  molecule  of  One  molecule  of  One  molecule  of 

Argentic  nitrate,         Sodic  Chloride,         Argentic  Chloride,      Sodic  nitrate. 

169i  58$  143  85 

parts  by  weight.  parts  by  weight.  parts  by  weight.  parts  by  weight 

228  228 


86  CHEMISTRY. 


This  white  precipitate  produced  in  this  experiment  pos- 
sesses some  special  interest  from  its  use  in  photography.  In 
fact  chloride  of  silver,  as  a  thin  film  upon  the  surface  of  the 
photographic  paper,  is  the  principal  substance  which,  by  its 
sensitiveness  to  light,  produces  the  photographic  picture, 
and  any  one  who  tries  the  experiment  last  described  will 
soon  observe,  upon  preserving  the  chloride  of  silver  so  pro- 
duced, that  it  rapidly  grows  dark  upon  exposure  to  sun- 
light. 

Bleaching-Powder. 

The  substance  known  as  bleaching-powder  may  be  spoken 
of  in  a  general  way  as  consisting  of  lime  saturated  with 
chlorine.  This  description  points  very  justly  to  the  method 
of  producing  the  substance,  but  gives  no  idea  of  the  chemi- 
cal arrangement  of  the  constituents.  Scheele  early  noticed 
that  chlorine  gas  possesses  decided  bleaching  power,  and 
the  French  chemist,  Berthollet,  soon  called  attention  to  the 
possible  applications  of  the  substance  in  the  bleaching  indus- 
tries. But  its  annoying  odor  made  it  impracticable  to  use 
chlorine  on  any  large  scale  in  the  state  of  gas,  and  forbade 
the  use  of  it  even  when  dissolved  in  water.  At  length, 
twenty  years  after  the  discovery  of  the  gas — that  is,  in  1798 
— the  plan  of  absorbing  chlorine  in  lime  was  hit  upon,  and 
here  may  be  discovered  the  beginnings  of  the  bleaching- 
powder  industry,  now  one  branch  of  the  alkali  trade,  the 
greatest  chemical  industry  conducted  by  man.  This  bleach- 
ing-powder, at  first  a  mere  chemical  curiosity,  is  now  manu- 
factured by  the  thousands  of  tons,  and  is  used  in  the  bleach- 
ing of  cotton  and  linen  goods,  both  in  the  form  of  cloth  and 
in  the  form  of  the  various  kinds  of  paper. 

In  another  place  (pp.  98,  99,  100,  101,)  reference  is 
made  to  the  vast  proportions  attained  by  the  alkali  indus- 
try; meaning  the  manufacture  of  certain  compounds  of 
sodium,  the  one  produced  in  largest  quantities  being  doubt- 
less sodic  carbonate  (N"aaCO3),  commonly  called  soda-ash. 
In  trade  this  substance  is  called  an  alkali  because  of  certain 


CHEMISTRY. 


alkaline  properties  it  possesses,  but  more  strictly  speaking  it 
is  called  a  salt— sometimes  an  alkaline  salt.  In  chemistry  the 
single  term  alkali  is  reserved  for  certain  compounds  called 
hydrates,  of  which  indeed  sodic  hydrate — having  the  for- 
mula NaOH,  and  often  called  caustic  soda — is  an  appropriate 
example.  This  latter  compound  is  at  present  manufactured 
on  a  large  scale  in  connection  with  soda-ash. 

The  alkali  trade  has  passed  historically  through  three 
well-marked  stages.  The  first  stage  is  the  ancient  one; 
in  it  sodic  carbonate  is  produced  from  the  ashes  of  sea 
weeds.  The  second  stage  is  that  of  the  ascendency  of  the 
Leblanc  process  of  making  sodic  carbonate  from  common 
salt.  The  third  stage,  the  Solvay  process,  also  called  the 
ammonia  process,  of  making  sodic  carbonate  from  common 
salt,  has  come  but  recently  in  vogue,  but  threatens  to  absorb 
the  entire  field. 

The  Leblanc  process  involves  at  least  three  great  depart- 
ments. In  the  first  department  sulphuric  acid  is  manufact- 
ured ;  this  acid  is  added  to  common  salt  and  as  a  result 
sodic  sulphate  and  hydrochloric  acid  are  produced;  the 
sodic  sulphate  is  carried  to  the  second  department,  where  it 
is  turned  into  sodic  carbonate — that  is,  soda  ash;  the  hydro- 
chloric acid  is  carried  to  the  third  department,  where  it  is 
turned  into  bleaching-powder.  This  production  of  hydro- 
chloric acid  and  bleaching-powder  contributes  somewhat 
toward  the  support  of  the  Leblanc  process,  thus  to  a  certain 
extent  offsetting  the  decided  merits  of  the  Solvay  process. 

In  the  production  of  bleaching-powder  the  first  step 
is  to  mingle  hydrochloric  acid  and  manganese  dioxide. 
Chlorine  gas  is  thus  generated,  much  as  it  is  when  the 
experiment  is  conducted  on  a  small  scale  as  already 
described.  The  chlorine  so  generated  is  passed  into  a 
chamber  provided  with  shelves  and  containing  slaked  lime. 
Hereupon  the  lime  absorbs  the  chlorine,  giving  rise  to  a 
new  substance  called  bleaching-powder — also  known  as 
chloride  of  lime.  From  what  has  been  said  it  is  evident 
that  chemists  know  perfectly  well  what  elementary  substances 


CHLORINE. 


89 


enter  into  this  compound.  But  there  are  decided  differ- 
ences of  opinion  as  to  the  exact  way  in  which  the  atoms  are 
arranged.  Bleaching-powder  is  generally  considered  to  be 
a  chemical  union  of  calcic  hypochlorite  and  calcic  chloride 
with  the  addition  of  calcic  hydrate.  The  following  may 
serve  as  a  formula  for  the  compound: 


CaCl2O2 

(Calcic  hypochlorite.) 


CaCl2 

(Calcic  chloride.) 


Ca02H2 

(Calcic  hydrate.) 


FIG.  19— Apparatus  for  producing  bleaching-powder  (by  passing  chlorine   gas, 
generated  in  A,  upon  quick-lime  spread  upon  the  shelves). 

The   use  of  bleaching-powder  offers  certain  advantages. 
The  following  are  some  of  them: 
— The  compound  is  itself  white. 

—It  is  a  powder  which  can  be  easily  handled,  packed  and 
transported. 

—With  reasonable  precautions  the  active  bleaching  agent, 
chlorine,  is  retained  by  the  powder  in  available  form  for  a 
considerable  length*  of  time. 
— The  liberation  of  this  chlorine  is  easily   effected.     The 


90 


CHEMISTRY. 


addition  of  almost  any  acid  will  accomplish  it;  even  the 
carbon  dioxide  of  the  atmosphere  will  suffice. 


FIG.  20.— Apparatus  for  "souring"  cotton  cloth  by  passing  it  into  dilute  acid,  before 
submitting  it  to  the  action  of  bleaching-powder. 

— In  actual  use  in  the  process  of  bleaching,  the  entire 
amount  of  chlorine  originally  stored  up  in  the  powder  may 
be  liberated  in  contact  with  the  goods  to  be  bleached, 


CHLORINE.  91 


In  the  bleaching  of  cotton  goods  chlorine  is  not  the  only 
agent  relied  upon,  though  it  seems  to  be  an  essential  one. 
At  least  three  other  substances  are  employed  to  contribute 
to  the  bleaching.  Each  of  them  either  removes  some  colors 
or  stains  from  the  goods  or  so  modifies  them  that  the  solu- 
tion of  bleach  ing-powder — one  of  the  last  agents  to  be 
employed — can  the  easier  finish  its  work.  The  three  sub- 
stances referred  to  are  milk  of  lime,  diluted  sulphuric  acid, 
and  sodic  carbonate,  also  called  soda-ash. 

The  pieces  of  cloth,  being  sewed  together  in  continuous 
strips  many  miles  in  length,  pass  from  one  liquor  to  another, 
with  washings  in  water  at  proper  times,  until  finally,  after 
being  fully  whitened  by  the  chlorine  preparation  and  then 
receiving  the  final  washing  in  water,  they  emerge  from  the 
works,  completely  bleached. 


READING   REFERENCES. 
Alkali  Trade,  in  its  Various  Branches. 

Clans,  C. — Chem.  News,     xxxviii,  263.     (Ammonia  soda.) 
Davis,  G.  B.— Chem.  News,     xxxii,  164,   174,  187,  198,  210,  238. 
Hargreaves,  J. — Chem.  News,     xlii,  322. 
Kingzett,  Charles  T.— The  Alkali  Trade.     London,  1877. 
Lunge,  G-. — Jour,  of  Chem.  Soc.  of  London,     xliv,  524,  528. 
Mactear,  J.— Chem.  News,     xxxv,  4,  14,  17,  23,  35;  xxxvii,  16. 
-    Schmidt,  T. — Chem.  News,     xxxviii,  203.     (Ammonia  soda.) 

Weldon,  W.— Chem.  News,     xlvii,  67,  79,  87.     (Present  condition  of 
soda  industry.) 

Bleaching-Powder. 

Jurisch,  K.— Jour  of  Chem.  Soc.  of  London,     xxxi,  350. 

Kingzett,  C.  T.— loc.  cit.     xxviii,  484. 

Kopfer,  F.— loc.  cit. — xxviii  713. 

Lunge,  G. — Chem.  News,     xliii,  1. 

Stahlschmidt,  C. — Jour,  of  Chem.  Soc.  of  London,     xxxi,  279. 

Wolters,  "W. — loc.  cit.    xxviii,  404. 
Chlorine  Industry,  Future  of 

Hurter,  F. — Jour,  of  Chem.  Soc.  of  London,     xlvi,  225. 
Chlorine,  Preparation  of 

Berthelot— Annales  de  Chimie  et  de  Physique.     5  Ser,     xxii,  464. 


CHEMISTRY. 


Davy,  Sir  Humphry. 

Davy,  John. — Collected  "Works  and  Memoirs  of  Sir  H.  Davy.     London, 

1839. 

Paris,  John  A. — Life  of  Sir  Humphry  Davy.     London,  1831. 
Brougham,  H. — Lives  of  Men  of  Letters,  etc.     London,  1845.     p.  448. 
Cooke,  J.  P. — Scientific  Culture.     Boston,  1881.     p.  11. 

Salt  Mines  of  Europe. 

Harper's  Magazine,     i,  759. 

Scheele,  C.  W. 

Hoefer,  F.— Histoire  de  la   Physique  et  de  la  Chimie.     Paris,  1872. 
p.  497. 

Berthollet. 

Davy,  John — Memoirs  of  Sir  H.  Davy.     London,  1839. 


BROMINE.  93 


XII. 

BROMINE. 

IROMINE  is  an  elementary  substance  which  was 
first  recognized  as  such  in  the  year  1826.  It  was 
detected  by  Antoine  Jerome  Balard,  a  French 
chemist,  who,  at  the  age  of  twenty-four,  was  so 
fortunate  and  skillful  as  to  discover  this  interesting  substance. 
He  lived  at  Montpellier,  not  far  from  Marseilles,  and  but  a 
few  miles  from  the  Mediterranean.  The  waters  of  this  great 
inland  sea  contain  about  one  tenth  more  mineral  salts  than 
those  of  the  larger  oceans,  and  so  it  has  long  been  the  cus- 
tom along  the  southern  coasts  of  France  to  manufacture  salt 
from  them.  The  water,  being  drawn  from  the  sea  and 
pumped  into  successive  members  of  a  series  of  basins  or  res- 
ervoirs, evaporates  under  the  warm  rays  of  the  southern 
sun.  The  basins  are  about  a  foot  in  depth,  but  aggregate 
hundreds  of  acres  in  area.  Little  by  little  the  salt  separates 
from  the  water  and  is  raked  out  of  the  basins  and  transferred 
to  level  surfaces  called  tables.  After  this  principal  constit- 
uent is  removed  there  remains  a  strong  brine  called  bittern. 
While  experimenting  upon  this  bittern  Balard  was  struck  by 
a  peculiar  orange-red  coloration  of  great  intensity  which 
appeared  at  certain  stnges  of  his  work.  Upon  further  study 
he  was  able  to  demonstrate  that  this  color  was  due  to  an 
elementary  substance  hitherto  unrecognized.  Thus  he  had 
the  felicity  of  securing  for  his  name  permanent  renown  as 
one  of  the  few  philosophers  who  have  been  able  to  detect  a 
new  member  of  that  family  of  prime  and  fundamental 
materials  from  which  is  built  the  structure  of  the  universe. 
It  has  already  been  stated  that  the  elements  at  present 
acknowledged  are  about  seventy  in  number,  and  some  of 
these  were  known  to  the  ancients.  In  some  cases  a  single 
individual  has  been  able  to  recognize  several  new  ones;  thus 


94  CHEMISTRY. 


Scheele  has  already  been  mentioned  as  the  discoverer  of 
manganese,  barium  and  chlorine.  So  it  appears  that  while 
many  eminent  men,  by  conscientious  labor,  have  contributed 
to  the  building  of  the  science  of  chemistry  as  a  noble  and 
harmonious  edifice,  necessarily  but  few  of  them  can  possibly 
attain  the  specially  conspicuous  honor  of  having  their  names 
forever  associated  with  the  first  discovery  of  any  of  the  pri- 
mary elements.  An  interesting  story  is  told  of  the  eminent 
German  chemist,  Justus  von  Liebig,  in  connection  with  this 
particular  subject.  Some  years  before  Balard's  discovery 
there  was  sent  to  Liebig,  from  a  German  establishment  where 
salt  brines  were  employed,  a  flask  of  liquid — which  was 
afterward  found  to  contain  bromine,  or  at  least  to  be  very 
rich  in  bromine — with  the  request  that  he  examine  the  con- 
tents. The  general  appearance  of  the  substance  seemed  to 
be  that  of  chloride  of  iodine,  and  this  circumstance  led 
Liebig  to  neglect  making  a  more  searching  investigation. 
After  Balard  had  published  his  discovery  Liebig  perceived 
his  own  unfortunate  oversight,  and  occasionally,  of  course  not 
without  some  bitter  regret,  he  displayed  to  his  friends  this 
interesting  flask,  to  show  them  how  one  might  fail  to  make 
a  discovery  of  the  first  importance  by  reason  of  some  trifling 
oversight.* 

Distribution  of  Bromine. 

The  name  bromine  is  derived  from  a  Greek  word  (/3pw^o^, 
bromos,  a  bad  smell)  which  suggests  the  very  pungent  odor 
of  its  vapor.  The  substance  occurs  in  the  brine  of  the  ocean 
and  in  that  of  mineral  springs.  But  of  course  it  does  not 
exist  there  in  the  uncombined  form;  instead,  it  is  united  with 
certain  metals  in  the  form  of  bromides.  In  sea-water  the 
principal  bromide  is  bromide  of  magnesium  (MgBr2). 

Experimental  Preparation  of  Bromine. 

Bromine  may.be  prepared  by  any  one  who  is  willing  to 
take  a  little  trouble. 

*Schutzenber,ger,  Paul;  Traitede  Chimie  Generate,    Parts,  1930.    i,  375, 


BROMINE.  95 


Place  in  any  suitable  glass  vessel  a  small  amount  of 
manganese  dioxide,  some  potassic  bromide  (commonly  known 
as  bromide  of  potassium),  then  some  water,  and  finally  a 
small  quantity  of  hydrochloric  acid.  Bromine  is  almost 
instantly  liberated,  and  shows  its  presence  by  imparting  to 
the  liquid  an  orange  hue.  If  the  vessel  is  covered  lightly, 
and  then  gentle  heat  is  applied  to  it,  the  bromine  will  be 
expelled  from  the  liquid  and  will  appear  above  it  as  a  heavy 
vapor  of  a  rich  reddish-brown  color.  Some  care  'must  be 
exercised,  however,  in  conducting  this  experiment,  since  the 
vapor  is  very  irritating  to  the  eyes  and  also  to  the  throat, 
and  it  has  a  general  corrosive  effect  upon  most  substances 
with  which  it  comes  in  contact. 

Chemical  Properties  of  Bromine. 

In  its  chemical  relations  bromine  shows  very  decided 
resemblances  to  chlorine,  having  affinities  for  the  same  sub- 
stances, only  less  in  intensity.  Since  its  discovery  it  has  found 
a  considerable  number  of  uses.  Thus,  it  is  an  important  sub- 
stance in  the  processes  of  photography;  and  the  enormous 
expansion  and  growth  of  this  art  within  a  very  few  years 
has  required  in  the  aggregate  large  quantities  of  bromine. 
The  considerable  demand  for  bromine,  which  at  first  increased 
its  price,  has  produced,  as  might  have  been  anticipated,  a 
stimulating  influence  upon  the  manufacture  of  it.  This  has 
led  to  greatly  increased  production  of  the  substance,  not  only 
in  Europe  but  also  in  the  United  States.  In  Pennsylvania, 
Ohio  and  West  Virginia  it  has  become  an  important  article 
of  manufacture;  in  fact,  the  United  States  now  furnishes 
the  largest  proportion  of  the  entire  amount  of  the  material 
produced  in  the  world. 

One  of  the  most  important  compounds  of  bromine  is  that 
produced  by  its  union  with  silver.  We  refer  to  argentic 
bromide  (commonly  called  bromide  of  silver,  AgBr).  This 
substance  may  be  easily  produced  by  the  following  simple 
experiment. 


96 


CHEMISTRY. 


To  a  solution  of  potassic  bromide  in  water  add  a  water 
solution  of  argentic  nitrate;  a  white  or  yellowish-white  pre- 
cipitate immediately  appears. 


FIG.  21.— Louis  Jacques  Mand£  Dagruerre,  from  whom   the  daguerreotype  was 
named.    Born  at  Cormeilles,  France,  1789;  died,  1851. 

The  chemical   change   is   represented    by  the    following 
equation: 

KBr         -f-        AgNO3        =          AgBr          -f        KNO3 

One  molecule  of              One  molecule  of  One  molecule  of  One  molecule  of 

Potassic  bromide,  Argentic  nitrate,  Argentic  bromide,  Potassic  nitrate, 

119                           169£  187£  101 

parts  by  weight.              parts  by  weight.  parts  by  weight.  parts  by  weight. 


288k 

The  argentic  bromide  produced,  at  first  nearly  white  in 
color,  has   the  power  of  becoming  black  upon  exposure   to 


PLATE  IV.— Photographer  at  work  in  a  room  lighted  through  a  window  of  red 
glass.     (Red  glass  cuts  off  the  chief  actinic,  or  chemical,  rays  of  sunlight.) 


BROMINE.  97 


light,  and  it  is  this  important  property  which  makes  the  sub- 
stance suitable  for  use  in  the  process  of  photography. 

Again,  in  the  form  of  potassic  bromide,  bromine  has  had 
a  very  wide  and  beneficent  use  as  a  remedial  agent;  it  is 
largely  used  in  the  manufacture  of  the  salt  last  mentioned. 


READING  REFERENCE. 
Liebig,  His  Life-Work  in  Chemistry. 

Hofmann,  A.  W. — Jour,  of  Chem.  Soc.  of  London,     xxviii,  1065. 

7 


98  CHEMISTRY. 


XIII. 

IODINE,, 

ODINE  belongs  to  what  may  be  called  a  chemical 
family,  the  other  members  being  chlorine  and 
bromine.  All  three  of  these  elements  are  found 
in  sea-water,  but  in  very  different  quantities. 
Thus  chlorine  is  extremely  abundant ;  bromine  is  in  the  water 
in  minute  quantities,  while  iodine  exists  there  in  amounts 
that  are  exceedingly  small.  They  all  exist  as  salts,  of  which 
of  course  chloride  of  sodium  is  by  far  the  most  abundant. 
It  has  already  been  shown  that  bromine  is  obtained  from  sea- 
water,  after  enormous  amounts  of  the  water  have  been  con- 
centrated by  evaporation.  But  iodine,  the  third  element  of 
the  group,  exists  in  sea-water  in  quantities  so  very  minute 
that  it  cannot  be  directly  extracted  from  it  at  any  practicable 
cost.  Even  the  concentration  method  just  alluded  to  is  not 
applicable  in  the  case  of  iodine.  It  happens,  however,  that 
sea-weeds  have  the  power  of  extracting  from  sea-water  even 
the  exceedingly  minute  amount  of  iodine,  or  of  iodides,  that 
the  water  contains  ;  and,  moreover,  when  sea-weeds  are 
burned,  iodides  are  fo:md  in  their  ashes. 

The  Discovery  of  Iodine. 

The  discovery  of  iodine  is  associated  with  the  history  of 
certain  of  the  most  important  and  interesting  products  of  the 
chemical  arts.  It  also  has  a  striking  connection  with  some  of 
the  political  and  military  affairs  of  France,  and,  indeed,  of 
Europe,  in  the  early  years  of  the  present  century.  Finally, 
its  great  usefulness  to  mankind  is  in  marked  contrast  with 
the  misfortunes  that  overtook  its  discoverer. 

The  discovery  of  iodine  is  directly  referable  to  the  old 
soda  industry.  The  term,  soda  is  a  general  one,  and  it  was 


IODINE. 


99 


formerly  used  to  include  several  different  chemical  compounds 
manufactured  from  the  ashes  of  sea-weed.  Decidedly  the 
most  important  of  these  is  sodic  carbonate.  This  substance 
has  a  well  marked  alkaline  reaction,  and  although  not  an 
alkali  in  the  strictest  chemical  sense,  it  is  yet  the  principal 
product  of  that  greatest  of  all  the  chemical  industries,  known 
as  the  alkali  trade.  (See  pp.  86  and  88.)  During  the  last  sixty 
years  and  after  many  early  trials  and  failures,  the  production 


FIG.  22.— Catherine  the  harvest  of  sea-weed  for  the  manufacture  of  soda-ash. 

of  the  various  alkaline  compounds  of  sodium  has  risen  to 
enormous  proportions,  such  that  in  England,  alone  the  annual 
product  of  sodic  carbonate,  the  principal  one,  is  probably  more 
than  six  hundred  thousand  tons.  This  vast  amount  of  alkali 
is  consumed  by  civilized  peoples  in  some  of  their  most  exten- 
sive industries,  such  as  the  manufacture  of  soap  and  of  gla^s, 
and  in  many  processes  of  bleaching.  The  extension  of  these 
branches  of  business  has,  of  course,  gone  hand  in  hand  with 
the  increased  production  of  alkali.  Indeed,  on  the  one  side 
there  has  been  a  steady  diminution  in  price  and  on  the  other 
a  steady  increase  in  consumption  ;  probably  each  circum- 


100 


CHEMISTRY. 


stance  may  be  considered  as  both  cause  and  effect  of  the 
other.  Prior  to  1793,  however,  the  demands  for  alkali — 
vastly  smaller  than  to-day — were  all  satisfied  by  the  material 
obtained  from  the  ashes  of  marine  plants.  Thus  along  the 
coasts  of  Great  Britain,  France,  and  especially  of  Spain,  sea- 
weed of  various  kinds  was  gathered  as  a  very  important 
harvest.  Some  of  the  weed  was  used  as  a  fertilizer  of  the 
soil  ;  more  was  dried  and  burned  for  the  sake  of  the  ashes. 


FIG.  23.— Varieties  of  sea-weed  used  to  produce  varech. 

On  the  British  coast  the  ash  was  known  as  kelp  ;  that  pro- 
duced on  the  coasts  of  Normandy  was  called  varech,  and 
that  produced  on  the  Spanish  coast  went  by  the  name  of 
barilla. 

Now  one  of  the  important  indirect  effects  of  the  French 
Revolution  was  that  felt  by  the  consumers  of  the  old-fash- 
ioned alkali.  In  1793  an  embargo  was  put  upon  the  supply 
of  alkaline  ashes,  such  as  kelp  and  barilla,  into  France.  But 
the  French  demand  for  alkali  from  sea-weed — that  is,  sodic 
alkali,  was  very  much  stimulated  by  the  draft  upon  the  potas- 


IODINE.  101 


sic  alkali  for  the  preparation  of  the  great  amounts  of  salt- 
petre required  for  the  manufacture  of  gunpowder.  The 
immediate  effect,  therefore,  was  favorable  to  the  sudden 
development  of  an  invention  by  a  French  physician,  Leblanc, 
by  which  alkaline  compounds  of  sodium  could  be  manufact- 
ured independently  of  the  ashes  of  sea-weed — that  is,  from 
common  salt.  Notwithstanding  the  stimulus  of  the  political 
affairs  referred  to,  and  the  fostering  help  of  the  Government, 
the  complexity  of  the  Leblanc  process  was  such  that  it  was 
slow  in  gaining  a  foothold  as  a  practical  industrial  method. 
But  after  its  first  successful  establishment  as  a  regular  bus- 
iness, and  up  to  almost  the  present  day,  the  application  of 
this  process  has  continually  widened,  and  for  a  long  time 
the  method  held  undivided  sway  in  its  important  field. 

In  the  year  1811  Bernard  Courtois,  a  French  chemist,  was 
engaged,  just  as  other  manufacturers  were,  in  the  production 
of  nitrate  of  potash,  or  saltpetre,  for  use  in  gunpowder.  He 
also  manufactured  soda  from  varech.  In  order  to  separate 
the  alkali  from  the  varech  in  a  more  refined  condition  the 
raw  varech  was  subjected  to  a  very  careful  purification.  At 
certain  stages  of  his  experiments  Courtois  was  struck  with 
the  corrosion  of  his  copper  kettles  ;  he  also  observed  that  this 
corrosion  was  most  violent  with  certain  liquids  which,  upon 
the  addition  of  sulphuric  acid,  gave  rise  to  the  production  of 
a  magnificent  violet  vapor.  He  did  not  make  the  matter 
public,  however,  until  late  in  the  year  1813,  when  Ampere 
brought  the  substance  to  the  attention  of  Sir  Humphry  Davy, 
the  distinguished  English  chemist,  who  was  then  visiting 
Paris.  Davy  at  once  recognized  it  as  a  new  element  of  sim- 
ilar character  to  chlorine.  The  next  year,  1814,  the  substance 
was  carefully  investigated  by  Gay-Lussac,  who  gave  to  the 
world  a  very  full  description  of  its  properties,  -and  who  called 
it  iodine,  from  a  Greek  word  (loeid^g,  ioeides,  violet  colored), 
suggesting  the  striking  and  characteristic  color  of  its  vapor. 
The  political  events  of  1815  ruined  the  business  of  Courtois, 
and  he  sunk  into  poverty  from  which  he  was  not  able  to  re- 
cover, until  finally  he  died,  in  1838,  poor  and  almost  forgotten. 


102 


CHEMISTRY. 


Present  Sources  of  Iodine. 

Although  kelp,  varech  and  barilla  are  no  longer  used  for 
the  direct  purpose  of  aifording  alkali,  they  are  still  produced 
with  a  view  to  their  yielding  iodine.  On  the  rough  and 
stormy  coasts  of  Scotland,  Ireland,  France  and  Spain,  large 
quantities  of  sea-weeds  are  cast  ashore.  They  are  collected, 
they  are  dried  in  the  sun,  they  are  then  burned,  and  their 
ashes  are  employed,  but  principally  in  the  manufacture  of 
iodine.  Thus  on  the  coasts  of  Brittany  and  Normandy  the 
occupation  of  collecting  weeds  occupies  three  or  four  thou- 
sand families  for  the  larger  part  of  the  year. 

Experimental  Method  of  Preparing  Iodine. 

Iodine  may  be  prepared  in  a  manner  closely  resembling 
the  process  already  described  for  bromine — that  is,  by  placing 
in  a  suitable  glass  vessel  a  small  amount  of  manganese  diox- 
ide, some  potassic  iodide  (commonly  known  as  iodide  of 

potassium), then 
some  water,  and 
finally  a  small 
quantity  of  hy- 
drochloric acid. 
Iodine  is  almost 
instantly  liber- 
ated, and  shows 
its  presence  by 
imparting  to  the 
liquid  a  brown- 
ish color.  If  the 
vessel  is  cov- 
ered lightly  and 
then  gentle  heat 
FIG.  ~4. -Changing  iodine  to  a  violet  vapor  by  means  of  heat.  1S  applied  to  it 

the  iodine   will 

be  expelled  and  appear  in  the  vessel  above  the   liquid  as  a 
heavy  vapor  of  a  rich  violet  color.     This  vapor  readily  con- 


IODINE. 


103 


denses  on  the  upper  and  colder  portions  of  the  vessel  in  the 
form  of  minute  crystals  of  a  color  almost  black.  This  is 
almost  precisely  the  method  employed  on  the  large  scale  for 
the  production  of  iodine  from  kelp. 


Chemical  Properties  of  Iodine. 

The  chemical  characteristics  of  iodine  are  throughout 
closely  allied  to  those  of  chlorine  and  of  bromine,  only,  in 
general,  iodine  may  be  said  to  have  weaker  chemical  affinities 
than  either  of  the  other  two. 


FIG.  25.— Apparatus  used  in  the  manufacturing  process  for  obtaining  iodine.  The 
retorts  C,  C,  are  surrounded  by  sand  (sand-bath);  the  heat  drives  iodine,  in  form  of 
vapor,  Into  the  receivers,  A,  A,  where  it  solidifles. 

Iodine  produces  compounds  of  the  same  general  type  as 
the  others,  and  of  this  an  example  is  found  in  argentic  iodide. 
The  following  method  of  producing  it  can  be  followed  by 
almost  any  one.  Prepare  a  solution  of  nitrate  of  silver  in 
water,  and  then  add  a  water  solution  of  potassic  iodide  ;  a 
chemical  change  takes  place,  with  the  production  of  a  yellow- 
ish-white precipitate.  This  precipitate  is  argentic  iodide. 
Upon  exposure  to  sunlight  it  readily  changes  in  color,  becom- 
ing almost  black.  This  is  an  important  characteristic  and  is 
made  use  of,  as  is  the  same  property  possessed  by  argentic 


104  OHEMISTHT. 


bromide  and  also  by  argentic  chloride,  in  the  production  of 
the  photograph.  And  while  it  is  a  fact,  and  one  well  known, 
that  many  of  the  salts  of  silver  blacken  more  or  less  upon 
exposure  to  sunlight,  it  is  found  that  the  chloride,  the  bro- 
mide and  the  iodide  have  properties  particularly  fitting  them 
for  the  purposes  of  photography.  In  discussing  bromine, 
reference  was  made  to  the  influence  of  the  great  expansion 
of  the  photographic  business  ;  and  this  circumstance  has 
stimulated  the  demand  for  iodine  just  as  for  bromine.  It 
was  also  pointed  out  that  potassic  bromide  is  an  important 
remedial  agent ;  potassic  iodide  is  likewise  of  great  medicinal 
value. 

Starch  as  a  Test  for  Iodine. 

Iodine,  when  in  the  free  or  uncombined  condition,  has  a 
remarkable  and  very  peculiar  way  of  attaching  itself  to  gran- 
ules of  starch. 

This  property  may  be  demonstrated  by  a  simple  and  attract- 
ive experiment.  Thus,  if  starch  is  boiled  with  water  and  then 
the  hot  mass  is  poured  into  cold  water,  minute  particles  of 
starch  distribute  themselves  through  the  liquid.  If  to  this 
liquid  a  very  small  amount  of  free  iodine  is  added,  the  starch 
instantly  takes  on  a  deep  blue  color.  If  to  another  portion 
of  the  same  or  similar  starch  suspended  in  water,  iodine  is 
added  in  a  combined  form — that  is,  as  potassic  iodide,  for 
example — absolutely  no  change  of  color  is  detected.  These 
two  experiments  show  that  the  iodine  only  attacks  starch 
when  the  iodine  is  free  and  uncombined. 


READING  REFERENCES. 
Gay-Lussac. 

Davy,  John. — Memoirs  of  Sir  H.  Davy. 
Chlorine,  Bromine,  Iodine,  and  Fluorine. 

Mylius,  E.— Cliem.  News,     xxxiii,    244,    253;  xxxiv,   5,  13.  25,  33,  45, 

55,  66,  78,  86,  118,  139,  149,  166,  180,  188,  197,  215,  233. 
Iodine,  Manufacture  of 

Schmidt,  T. — Chem.  News,     xxxvii,  56. 

Stanford,  E.  C.  G.—Loc.  tit.     xxxv,  172. 
Iodine,  Discovery  of 

Davy,  John. — Memoirs  of  Sir  H.  Davy.     pp.  164-180. 

Paris,  John  A.-- Life  of  Sir  H.  Davy.     pp.  267-278. 


FLUORINE.  105 


XIV. 

FLUORINE. 

are  a  number  of  compounds  known  whose 
various  properties,  powers  of  chemical  interchange 
and  special  molecular  weights,  clearly  point  out 
the  existence  in  them  all  of  a  certain  peculiar 
element  analogous  in  many  respects  to  chlorine,  bromine  and 
iodine.  To  this  element  the  name  fluorine  has  been  given. 

Its  properties  in  these  combined  forms  have  been  Carefully 
studied  and  well  made  out.  Thus,  like  chlorine  and  its  family 
associates,  it  combines  with  hydrogen  to  form  an  acid, 
hydrofluoric  acid  (HF),  properly  comparable  with  the  acids 
formed  by  the  three  elements  last  discussed- 

Hydrofluoric  acid,  HF. 

Hydrochloric  acid,  HC1. 

Hydrobromic  acid,  HBr. 

Hydriodic  acid,  H  I. 

It  also  combines  with  the  metals  to  form  fluorides.  The 
best  example  of  these  fluorides  is  that  compound  in  which 
fluorine  most  commonly  occurs  in  nature — that  is,  fluor-spar, 
the  mineral  substance  whose  chemical  name  is  calcic  fluoride, 
and  whose  composition  is  expressed  by  the  formula  CaF8. 

Many  experiments  have  been  performed  for  the  purpose  of 
isolating  the  element  itself.  While  none  of  these  have  as 
yet  been  accepted  as  entirely  satisfactory,  some  recent  ones, 
especially,  have  been  so  far  successful  as  to  indicate  the 
probability  that  fluorine  is  a  colorless  gas.  It  seems  reason- 
able to  suppose  that  if  fluorine  were  a  solid  or  liquid  at 
ordinary  temperatures  some  processes  that  have  been  devised 
would  be  capable  of  producing  and  detaining  at  least  a  small 
quantity  of  the  elementary  substance,  and  that  from  this  the 
observer  would  be  enabled  to  recognize  and  discover  at  least 
some  of  the  properties  of  the  fluorine  itself. 


106  CHEMISTRY. 


Properties  of  Fluorine. 

The  property  above  all  others  that  is  characteristic  of 
fluorine  is  its  striking  affinity  for  silicon.  With  this  element 
it  readily  combines  under  a  variety  of  circumstances.  More 
wonderful  still,  the  compound  produced  with  it  is  a  gas. 
Now  in  general  the  compounds  of  silicon  are  solids.  These 
solids  are  many  of  them  familiarly  known  in  those  material.* 
which  constitute  the  principal  portions  of  the  stable  earth  on 
which  we  tread,  of  the  rock  beneath  it  and  of  the  enduring 
mountain  masses  that  here  and  there  pierce  through  the  soil 
and  raise  their  crests  above  the  general  level.  The  majority 
of  these  earthy  and  rocky  substances  are  silicates.  It  is  ap- 
parent, then,  that  the  compounds  of  silicon  are  types  of 
solidity  and  stability.  They  cannot  be  melted  except  in  the 
most  powerful  heating  appliances,  and  the  idea  of  their  being 
vaporized  by  heat  alone  is  quite  inconsistent  with  the 
ordinary  properties  recognized  in  them. 

So  then  it  seems  strange  and  almost  contradictory  that 
fluorine  should  have  the  power  of  attacking  compounds  that 
seem  to  be  the  embodiments  of  permanency  itself — yet  it 
readily  does  so.  Thus,  if  hydrofluoric  acid  comes  in  contact 
with  silicon,  whether  that  substance  is  in  combination  as  sand 
or  as  hard  rocky  minerals,  the  fluorine  atoms  pluck  out  the 
silicon  and  then  they  fly  away  together  in  the  form  of  gas  or 
vapor.  Again,  hydrofluoric  acid  may  be  spoken  of  as  the 
unique  agent  that  readily  attacks  glass,  and  dissolves,  and 
even  destroys,  this  ordinarily  unchangeable  substance. 

Finally,  there  may  be  added  what  can  be  said  of  no  other 
dement;  namely,  that  fluorine  is  not  known  to  form  any  com- 
pound with  oxygen. 

Discovery  of  Hydrofluoric  Acid. 

It  is  not  easy  to  refer  the  first  knowledge  of  fluorine  to 
any  particular  discoverer.  Perhaps,  however,  renewed  men- 
tion of  the  ingenious  Scheele  is  not  out  of  place  here ;  for  it 


FLUORINE. 


107 


seems  to  have  been  he  who  for  the  first  time,  and  as  early  as 
1771,  recognized  hydrofluoric  acid  as  a  special  acid.  He 
called  it  fluoric  acid,  but  he 
did  not  obtain  a  correct  idea 
of  its  composition.  Scheele 
prepared  the  acid  from  a  well- 
known  mineral,  fluor-spar,  and 
by  the  addition  of  sulphuric 
acid.  This  operation  cannot 
be  performed  to  advantage  in 
a  glass  or  porcelain  vessel,  for 
they  contain  silicon,  and,  as  has 
been  suggested  already,  sili- 
cious  matters  are  freely  attacked  by  the  acid  produced.  The 
decomposition,  therefore,  is  commonly  conducted  in  a  retort 
of  lead,  or  in  one  of  platinum,  and  the  acid  produced  is  col- 
lected in  a  receiver  also  constructed  of  one  of  these  metals. 

The  chemical   change   is    represented    by  the   following 
equation  : 


FIG.  26. — Platinum  retort  and  receiver 
shown  with  its  several  parts  separated. 


CaF2        -f 

H2SO4 

2HF 

f      CaSO4 

One  molecule  of 

One  molecule  of 

Two  molecules  of 

One  molecule  of 

Calcic  fluoride, 

Sulphuric  acid, 

Hydrofluoric  acid, 

Calcic  sulphate, 

78 

98 

40 

136 

parts  by  weight 

parts  by  weight. 

parts  by  weight. 

parts  by  weight. 

176 


176 


Ordinarily  the  product  is  a  liquid,  and  consists  of  water 
holding  in  solution  the  acid  (HF).  It  is  possible,  however, 
to  prepare  the  acid  free  from  water  and  still  in  a  liquid 
form. 

But  in  this  condition  it  is  one  of  the  most  dangerous,  pois- 
onous and  corrosive  substances  known.  It  produces  painful 
burns  if  it  falls  upon  the  flesh,  and  fatal  results  have  been 
known  to  follow  injuries  received  from  it.  Thus,  in  1869 
Professor  Nickles,  an  eminent  French  chemist,  died  from 
injuries  sustained  by  the  accidental  inhalation  of  hydrofluoric 
acid  vapor  while  studying  the  properties  of  the  substance. 


108 


CHEMISTRY. 


Etching  Glass  by  Hydrofluoric  Acid. 

The  effect  of  hydrofluoric  acid  upon  glass  may  be  shown 
in  attractive  form,  and  without  much  difficulty  or  danger,  by 
the  help  of  a  small  dish  of  lead  and  a  plate  of  glass  to  cover 
it.  These  being  provided  the  experiment  may  be  conducted 
somewhat  as  follows:  Melt  a  little  beeswax  upon  the  glass  so 
that  the  wax  may  form  a  thin  film  upon  one  side  of  it.  Then 
allow  the  wax  to  cool  and  harden.  Next,  by  use  of  any  con- 
venient pointed  instrument,  draw  some  sketch  or  design  deep 
in  the  wax — in  fact,  to  the  surface  of  the  glass.  Next  place 
some  powdered  fluor-spar  in  the  leaden  dish,  and  add  to  it 

some  concentrated 
sulphuric  acid.  Now 
cover  the  dish,  with 
the  glass  already 
prepared,  in  such  a 
way  that  the  sketch 
or  design  is  turned 
downward  so  as  to 
receive  the  fumes  of 
hydrofluoric  acid  as 
they  rise  from  the 

FIG.  27. —Platinum  retort  and  receiver  shown  as  ar-   mixture  in  the  dish 
ranged  for  production  of  hydrofluoric  acid  (HF). 

It  is  easily  under- 
stood from  what  has  been  said  already  that  the  hydrofluoric 
acid  will  attack  the  glass,  carrying  away  some  of  its  silicon 
in  the  form  of  gas  or  vapor.  As  a  result  of  this  action,  minute 
channels  are  formed  in  the  glass.  When  the  experiment  is 
thought  to  be  sufficiently  advanced  the  wax  may  be  removed 
from  the  plate  by  melting  it  off  or  otherwise  ;  thereupon  it 
will  be  discovered  that  the  glass  has  actually  become  etched 
or  engraved  by  the  hydrofluoric  acid  gas. 

In  1788  Puymaurin  presented  to  the  French  Academy  of 
Sciences  such  a  glass  plate,  upon  which  there  was  a  beautiful 
fluoric  etching  representing  Chemistry  and  Genius  weeping 
at  the  tomb  of  Scheele,  who  had  contributed  so  much  to  the 


FLUORINE.  109 


history  of  hydrofluoric  acid.  "This  work,"  says  Hatty,  "was 
of  interest  to  the  Academy  on  account  of  the  fitness  of  the 
subject  as  well  as  the  elegance  of  its  execution." 

Practical  Application  of  Hydrofluoric  Acid. 

Hydrofluoric  acid,  formerly  a  mere  chemical  curiosity,  has 
now  become  a  familiar  article  upon  the  shelves  of  the  drug- 
gists. It  is  sold  in  gutta-percha  bottles  with  rubber  stoppers. 
It  is  often  used  by  jewelers  to  correct  errors  in  the  applica- 
tion of  silicious  enamels  upon  their  work.  Thus,  if  the 
enamel  has  been  incorrectly  placed,  it  may  be  removed  by 
hydrofluoric  acid  and  afterward  a  new  portion  may  be  intro- 
duced in  the  proper  position.  Again,  it  is  largely  used  in  the 
decoration  of  artistic  glass  objects,  such  as  globes  for  gas 


FIG.  28.— Leaden  tray  and  glass  plate.  The  tray  is  Intended  to  receive  the  materials 
for  production  of  hydrofluoric  acid  ;  the  plate  is  represented  as  covered  with  a  var- 
nish, through  which  a  sketch  has  been  drawn,  preparatory  to  etching. 

chandeliers,  and  the  multitude  of  articles  of  table  glass-ware. 
In  engraving  such  objects  they  are  first  covered  with  a 
suitable  varnish  that  will  resist  the  hydrofluoric  acid,  then  the 
design  is  drawn  through  the  varnish  with  a  sharp  needle; 
afterward  the  article  is  exposed  to  the  gas  and  etched  in  a 
manner  similar  to  that  already  described. 


READING   REFERENCES. 
Hydrofluoric  Acid. 

Gore,  G.— Jour,  of  Chem.  Soc.  of  London,     xxii,  368. 
Fluorides. 

Fremy,  E.— Annales  de  Chimie  et  de  Physique.     3  Ser.     xlvii,  5. 
Fluorine,  Isolation  of. 

Moissan,  H.— Chem.  News,    liv,  36,  51,  80. 


110  CHEMISTRY. 


XV. 

OXYGEN. 

|XYGEN  may  justly  claim  a  high  degree  of  impor- 
tance as  a  subject  for  the  study  alike  of  the  pro- 
fessional chemist  and  the  casual  reader.  This 
importance  depends  upon  a  variety  of  considera- 
tions. Among  them  are  the  surpassing  abundance  of  the 
substance  itself,  the  great  number  of  compounds  into  which 
it  enters,  the  activity  of  its  chemical  powers,  and  finally,  the 
interesting  circumstances  under  which  its  distinct  recognition, 
or,  as  perhaps  we  may  say,  its  discovery,  was  attained. 

Its  great  abundance  has  been  pointed  out  already  in  the 
declaration  that  oxygen  makes  up,  by  weight,  fully  one  half 
of  our  terrestrial  globe — including  earth,  ocean  and  air.  The 
air  is  about  one  fifth  oxygen  by  weight ;  all  water,  wherever 
existing,  is  sixteen-eighteenths  oxygen  by  weight,  while 
quartz,  sand,  and  other  similar  wide-spread  and  most  com- 
monly occurring  mineral  matters  are  a  little  more  than  one 
half  oxygen.  Other  solid  matters  than  the  rocks,  such  as 
most  parts  of  the  material  structures  of  animal  and  vegetable 
beings,  contain  oxygen  as  an  important  constituent  element. 
While  thus  we  have  scanned  the  great  multitude  of  sub- 
stances spread  immediately  about  us  by  the  hand  of  nature, 
and  found  oxygen  in  them  all,  it  is  none  the  less  true  that 
oxygen  is  an  important  factor  in  artificial  products — that  is, 
those  resulting  from  man's  manufacturing  operations. 

Chemical  Activity  of  Oxygen. 

Again,  oxygen  plays  a  part  of  exceeding  activity  in  some 
of  the  grandest  chemical  processes  of  nature  and  of  the  arts. 

For  example,  it  is  essential  to  the  vital  processes  of  all 
animals.  Wherever  a  living  being  inhales  the  breath  of  life, 
whether  from  the  fresh  air  of  the  mountain  tops,  or  from  the 


OXYGEN.  HI 


populous  streets  of  the  swarming  metropolis,  or  from,  the  sol- 
itary deck  of  the  bark  that  creeps  with  the  ocean's  currents, 
or  wherever  the  humbler  servants  of  man's  table  find  their 
way  through  unexplored  depths  of  the  ocean  and  pluck  from 
its  waves  the  modicum  of  life-giving  gas  dissolved  within  them, 
there  is  this  wonderful  agent,  which  has  no  substitute,  sus- 
taining by  active  processes,  truly  chemical,  that  vitality  of 
man  or  of  beast  which  gives  to  nature  its  forms  of  highest 
beauty  and  most  admirable  intelligence. 

Again,  oxygen  is  the  necessary  agent  in  all  ordinary  com- 
bustions. So  wherever  a  fagot,  glowing  beneficently  in  a 
sparsely  peopled  forest,  helps  to  sustain  man's  vital  spark  ;  or 
where,  in  a  highly  civilized  community,  the  fires  on  the  altars 
of  modern  industry  draw  from  the  flinty  rocks  the  metals  that 
serve  to  give  employment  to  millions  of  children  of  toil ; 
there  oxygen  is  ever  active,  the  true  supporter  of  the  com- 
bustion of  all  those  flames  which  in  the  past  have  served  as 
signs  of  life  and  civilized  activity,  and  which  are  still  the 
best  symbols  of  vitality  and  intelligence. 

The  Discovery  of  Oxygen. 

The  first  discovery  of  oxygen  is  usually  attributed  to  Dr. 
Joseph  Priestley,  an  English  clergyman  and  student  of  nat- 
ural science.  He  lived  in  a  time  when  men's  minds  all  over 
Europe  were  strongly  drawn  toward  the  pursuit  of  chemical 
knowledge.  In  fact,  at  almost  the  same  moment  that  Priestley 
was  enthusiastically  conducting  his  experiments  Scheele  was 
also  producing  oxygen  in  his  apothecary's  chamber  in  Sweden. 
And  the  brilliant  Lavoisier,  prominent  among  the  men  of 
distinction  who  thronged  the  gay  capital  of  France,  was  also 
working  in  the  same  direction ;  it  was  he  who  said  about 
oxygen,  in  one  of  his  own  chemical  works  :  "  Cet  air  que  nous 
avons  decouvert  presque  en  meme  temps,  Dr.  Priestley,  M. 
Scheele  et  moi,"  so  that  he  is  sometimes  declared  by  his 
enthusiastic  countrymen  to  be  entitled  to  the  merit  of  the 
earliest  discovery  of  this  most  magnificent  of  elements. 


FIG.  29.— Joseph  Priestley. 


Born  near  Leeds,  England,  March  13, 1T33 :  died  in  Northum- 
berland, Pa.,  February  6, 1804, 
(112) 


OXYGEN.  113 


Priestley's  life  included  ample  materials  for  a  romance.  On 
-the  one  hand,  the  ingenious  discoverer  in  physics  and  chem- 
istry, and  the  friend  of  that  Benjamin  Franklin  who  was 
then  minister  at  the  brilliant  court  of  France  from  a  handful 
of  colonies  that  appeared  capable  of  being  plucked  up  by  the 
roots,  but  were  instead  destined  to  grow  to  an  unrivalled  em- 
pire— himself  a  figure  in  a  romance  ;  and,  on  the  other  side, 
a  preacher  to  a  dissenting  congregation  ;  a  victim  of  public 
odium  for  his  liberal  opinions  on  religious  and  political  sub- 
jects ;  his  house  set  on  fire  by  a  mob,  his  apparatus  wrecked, 
his  library  cast  to  the  winds ;  finally,  an  emigrant  with  his 
wife  and  children  to  a  village  in  Pennsylvania,  then  almost  un- 
known, whose  little  burial-ground  still  gives  his  bones  repose ; 
these  are  but  brief  suggestions  of  the  trials  of  this  perturbed 
spirit,  in  his  life  "sadly  driven  about  and  tossed,"  now 
cherished  as  one  of  those  who  in  the  realm  of  thought  has 
made  no  mean  contribution  to  the  glory  of  the  English 
name. 

Dr.  Priestley  prepared  oxygen  from  red  precipitate  of  mer- 
cury, a  substance  now  designated  by  the  name  mercuric  oxide 
and  by  the  formula  HgO.  Heating  this  substance  in  a 
receiver,  and  by  means  of  a  burning-glass  or  lens,  he  observed 
that  a  peculiar  kind  of  air  was  evolved.  He  further  discov- 
ered that  this  air  had  an  unusually  stimulating  influence  upon 
burning  bodies,  and  was  well  suited  for  the  respiration  of 
living  animals.  Priestley's  prime  experiment  was  performed 
on  the  1st  day  of  August,  1774;  a  date  which  may  be  accepted 
as  almost  the  birthday  of  modern  chemistry. 

Like  many  other  great  discoverers,  Priestley  was,  to  a  cer- 
tain degree,  anticipated.  Thus  a  certain  John  Mayow,  an 
English  physician,  fully  a  hundred  years  before  the  time  of 
Priestley's  experiment,  enunciated  the  doctrine  that  the  at- 
mosphere contains  an  air  in  a  certain  sense  the  essential  food 
of  animal  life  and  of  flame.  But  these  wonderful  views  ot 
Mayow,  brought  forward  too  early  for  the  state  of  thought 
at  his  time,  lay  dormant  and  unproductive  for  an  entire 
century. 

8 


114  CHEMISTRY. 


First  Method  of  Preparing  Oxygen. 

Oxygen  may  be  prepared  in  many  ways,  but  only  two  need 
receive  attention  here.  The  first  method  is  Priestley's.  If 
the  red  oxide  of  mercury  is  heated  over  a  powerful  gas  flame 
and  in  a  tube  of  not  easily  fusible  glass,  the  oxygen  passes 
from  the  metal,  and  may  be  carried  by  any  small  conducting 
tube  into  a  convenient  receiver  filled  with  water  and  standing 
in  the  pneumatic  trough.  If  the  gas  so  collected  is  tested  by 
means  of  a  candle  having  only  a  spark  on  its  wick,  the  oxy- 
gen is  readily  recognized  by  the  fact  that  the  taper  promptly 
bursts  into  a  full  and  brilliant  flame.  This  method  is  of  his- 
torical interest  chiefly,  though  it  may  well  attract  some  atten- 
tion from  the  simplicity  of  the  chemical  change  involved. 
Thus  this  change  is  represented  by  the  following  equation  : 

2HgO  healed  O2  +  2Hg 

Two  molecules  of  One  molecule  of  Two  atoms  of 

Mercuric  oxide,  Oxygen,  Mercury, 

432  32  400 

parts  by  weight.  parts  by  weight.  parts  by  weight. 


432  .  432 

A  word  about  the  pneumatic  trough  is  not  out  of  place 
here,  because  this  useful  contrivance  was  the  invention  of 
Priestley.  The  name  may  be  appropriately  applied  to  almost 
any  vessel  of  water  in  which  may  stand  the  open  mouth  of  a 
bell-glass  suitable  for  containing  gas.  The  water  serves  at 
once  to  seal  the  mouth  of  the  jar,  and  also  to  afford  a  mate- 
rial through  which  the  exit  tube  of  an  appliance  may  be 
dipped,  and  through  which  also  the  gas  from  the  tube  may 
freely  and  conveniently  flow  into  the  bell-glass.  Before 
Priestley's  time  gases  had  been  collected  in  bladders  or 
varnished  bags,  but  the  new  contrivance  furnished  a  much 
superior  means  of  detecting  small  quantites  of  gas  and 
working  with  them. 

Again,  for  all  the  ordinary  purposes  of  experimenting  with 
gases,  no  appliance  superior  to  that  of  Priestley  has  yet  been 
devised. 


OXYGEN.  115 


Second  Method  of  Preparing  Oxygen. 

The  second  method,  and  that  oftenest  pursued,  employs  a 
salt  not  known  in  Priestley's  time.  This  salt  is  called  potassic 
chlorate,  and  is  represented  by  the  formula  KC1O3. 

This  substance,  when  heated,  evolves  a  large  amount  of 
oxygen,  but  it  does  so  with  almost  explosive  violence. 

The  chemical  change  is  represented  by  the  following  equa- 


2KC\O3  heated  2KC1  +  3O2 

Two  molecules  of  Two  molecules  of  Three  molecules  of 

Potassic  chlorate,  Potassic  chloride,  Oxygen, 

245  149  96 

parts  by  weight.  parts  by  weight.  parts  by  weight. 

245  245 

On  the  other  hand,  if  the  potassic  chlorate  is  mixed  with 
about  one  third  of  its  weight  of  the  earthy  mineral  known 
as  black  oxide  of  manganese  (but  called  by  the  chemist, 
manganese  dioxide),  the  mixture  when  heated  evolves  oxygen 
more  slowly  and  continuously  than  the  chlorate  alone — and  it 
does  it  at  a  lower  temperature.  Strangely  enough,  however, 
the  manganese  dioxide  appears  to  take  either  no  chemical 
part  in  the  operation,  or  else  only  a  very  obscure  one.  Indeed, 
some  other  oxides  will  serve  the  same  purpose,  while  they 
likewise  appear  to  undergo  no  easily-detected  chemical  change. 

In  this  method,  as  in  the  other,  the  oxygen  gas  produced 
may  be  collected  in  a  bell-glass  over  the  pneumatic  trough, 
and  afterward  its  nature  may  be  demonstrated  as  before  by 
means  of  the  taper  having  a  spark  upon  it. 

The  Properties  of  Oxygen. 

It  has  been  the  custom  of  chemists  to  say  of  oxygen  that 
it  is  a  permanent  <jas.  The  force  of  this  expression  is  found 
in  the  fact  that  until  recently  all  attempts  to  liquefy  it  were 
futile.  But  recent  experiments,  with  apparatus  capable  of 
subjecting  it  at  once  to  more  intense  cold  and  to  greater 
pressure  than  were  ever  before  employed,  seem  to  demon- 


116  CHEMISTRY. 


strate  that  it  will  turn  to  a  liquid  when  these  conditions  are 
carried  to  a  sufficient  extreme. 

That  oxygen  is  colorless  and  odorless  appears  plain  from 
the  properties  of  the  atmospheric  air  throughout  which  this 
gas  is  thoroughly  diffused  and  intimately  intermingled, 
although  it  constitutes  but  one  fifth  of  it. 


FIG.  30. — The  rays  of  sunlight  concentrated,  by  a  lens,  upon  a  diamond  placed  in 
oxygen  gas,  with  a  view  of  proving  the  combustibility  of  the  gem. 


Chemical  Properties  of  Oxygen. 

Of  the  chemical  powers  of  oxygen  the  most  striking  and  im- 
portant seems  to  be  its  marked  tendency  to  combine  with  other 
elementary  substances.  In  many  cases  this  combination  does 
not  commence  except  when  the  substances  are  heated.  Thus 
the  noble  buildings  of  a  city  are  every  day  and  every  night 


OXYGEN. 


117 


continuously  and  harmlessly  bathed  within  and  without  by 
that  same  oxygen  that,  in  time  of  conflagration,  is  ready 
chemically  to  combine  with  their  elements,  and  as  a  result  to 
reduce  the  metropolis  to  ashes.  But  such  combination,  once 
inaugurated,  often  itself  affords  sufficient  heat  not  only  to 
make  the  process  continue,  but  also  to  generate  that  flame  or 
fire  which  is  the  token  of  what  is  ordinarily  called  combustion. 


FIG.  31.— The  burning  of  a  spiral  of  iron  wire  in  a  jar  of  oxygen  gas. 

In  this  view,  oxygen  is  often  spoken  of  as  a  supporter  of 
combustion.  That  this  property,  known  to  be  associated 
with  the  atmospheric  air,  does  in  fact  reside  in  the  oxygen 
of  it,  is  to  some  extent  proved  by  the  more  rapid  and  brilliant 
combustion  of  the  candle  in  pure  oxygen. 

Another  interesting  experiment  is  performed  when  a  piece 
of  charcoal,  which  may  be  supported  on  a  wire,  is  burned  a 
little  so  as  to  acquire  a  spark  and  then  is  dipped  in  oxygen 
gas.  The  single  coal  would  soon  cease  to  burn  in  atmos- 


118  CHEMISTRY. 


pheric  air,  but  it  burns  readily  and  brilliantly  in  pure 
oxygen. 

Even  the  diamond,  the  most  compact  and  imperishable 
form  of  carbon  known,  may  burn  in  pure  oxygen  gas  just  as 
the  most  humble  piece  of  coal  does,  and  the  relationship  of 
the  gem  to  the  commonplace  fuel  is  proved  by  this  exper- 
iment. 

Still  another  experiment  in  the  same  direction  may  be  con- 
ducted with  sulphur.  For  this  purpose  a  fragment  of  sulphur 
set  on  fire  may  be  dipped  in  a  jar  of  pure  oxygen.  The  sul- 
phur burns  with  vastly  increased  rapidity,  and  with  a  violet 
tiame  much  more  brilliant  than  that  of  sulphur  burning  in  air. 

Again,  some  substances  not  ordinarily  considered  combus- 
tible will  burn  in  oxygen  gas.  Thus  a  bundle  of  iron  wire, 
to  which  a  little  lighted  chip  is  attached,  itself  takes  fire  and 
burns  brilliantly  when  dipped  into  oxygen  gas. 

The  Products  of  Combustions  in  Oxygen. 

As  a  necessary  result  of  the  combustion  of  substances  in 
oxygen  there  are  produced  a  multitude  of  compounds  called 
oxides. 

This  is  true  of  the  candle,  which  consists  mainly  of  carbon 
and  hydrogen.  When  the  candle  burns  these  two  substances 
change  into  oxides.  The  carbon  produces  carbon  dioxide, 
whose  formula  is  CO2 ,  and  which  is  familiarly  known  as  car- 
bonic acid  gas.  This  oxide,  it  is  true,  is  not  easily  recognized 
by  the  ordinary  observer,  because  it  is  an  invisible  gas;  but  the 
chemist  can  prove  that  it  is  in  fact  the  product  of  this  com- 
bustion. At  the  same  time  the  hydrogen  produces  an  oxide 
whose  formula  is  H2O,  which  will  be  recognized  as  the  chem- 
ical expression  for  water.  And  so  water  is  in  fact  produced, 
though  in  the  form  of  vapor,  by  the  burning  candle. 

Charcoal  is  composed  almost  entirely  of  what  the  chemist 
calls  carbon,  and  when  it  burns  it  produces  the  oxide  called 
carbon  dioxide  (CO2).  This  is  the  same  invisible  gas  that 
has  already  been  declared  to  be  produced  when  the  carbon 


OXYGEtf.  113 


of  the  candle  is  burned,  and  in  this  case,  as  in  the  other,  it  is 
easy  for  the  chemist  to  prove  its  presence. 

In  the  case  of  carbon,  the  chemical  change  is  represented 
by  the  following  equation : 

C  +  Oa  CO2 

One  atom  of  One  molecule  of  One  molecule  of 

Carbon,  Oxygen.  Carbon  dioxide, 

12  32  44 

parts  by  weight.  parts  by  weight.  parts  by  weight. 


44  44 

And  likewise,  when  iron  is  burned,  there  is  formed  an  oxide 
whose  composition  is  expressed  by  the  formula,  Fe3O4 ;  (to 
this  substance  the  chemical  name  ferroso-ferric  oxide  is 
applied). 

So  when  sulphur  is  burned,  sulphur  dioxide  is  formed 
(SO,). 

In  this  case  the  chemical  change  is  represented  by  the  fol- 
lowing equation : 

S  -f-  O2  SO2 

One  atom  of  One  molecule  of  One  molecule  of 

Sulphur.  Oxygen,  Sulphur  dioxide, 

32  32  64 

parts  by  weight.  parts  by  weight.  parts  by  weight. 


64  64 

Ozone. 

* 

Ozone  is  a  peculiarly  active  form  of  oxygen.  .  It  is  believed 
to  have  the  formula  O3,  while  ordinary  oxygen  has  the  for- 
mula OQ.  Now  the  ozone  easily  parts  with  one  atom  of 
oxygen,  which  in  its  nascent  or  uncombined  state  is  ready 
to  combine  at  once  with  a  great  many  substances.  Under 
these  circumstances  it  manifests  the  same  anomalous  features 
as  those  described  under  hydrogen  dioxide  (see  page  124) ; 
that  is,  it  tends  to  add  oxygen  to  certain  substances  and  to 
withdraw  oxygen  from  others. 

Ozone  is  produced  in  many  ways,  one  of  the  best  being 


120  CHEMISTRY. 


the  steady  discharge  of  what  is  called  machine  electricity 
through  the  atmospheric  air  or  pure  oxygen  gas.  The  dis- 
charge, however,  must  be  silent,  and  not  in  the  form  of  sparks. 

Ozone  is  also  produced  by  certain  processes  of  slow  oxi- 
dation ;  thus,  when  a  piece  of  phosphorus  is  exposed  to  the 
air  at  ordinary  temperatures,  it  gradually  but  continually 
oxidizes.  This  oxidation  is  always  attended  by  the  pro- 
duction of  ozone. 

Ozone  is  believed  to  be  formed  in  the  atmosphere  in 
minute  quantities  by  the  mere  process  of  evaporation  of 
water. 

Properties  of  Ozone. 

Ozone  is  a  colorless  gas  at  ordinary  temperatures,  but  at 
very  low  temperatures  it  condenses  to  a  steel-blue  liquid. 
It  liquefies  much  more  easily  than  ordinary  oxygen  does. 

Ozone  is  an  extremely  powerful  oxidizing  agent,  instantly 
forming  oxides  of  certain  metals,  like  silver,  that  in  ordinary 
air  long  retain  their  bright  metallic  surfaces.  It  is  also  a 
powerful  bleaching  agent,  decomposing  and  whitening  cer- 
tain vegetable  and  animal  substances  with  great  promptness. 
Many  experiments  have  been  made  with  the  view  of  employ- 
ing ozone  in  bleacheries,  for  the  purpose  of  whitening  cotton 
and  linen  goods.  No  successful  results  have  been  reported, 
notwithstanding  the  general  belief  that,  in  the  old  methods  of 
grass  bleaching,  the  ozone  produced  in  small  quantities  by 
the  sun-light  and  evaporation  of  moisture  was,  in  fact,  the 
true  bleaching  agent. 

The  molecular  constitution  of  ozone  is  believed  to  be  that 
suggested  by  the  expression  O3  or, 


a  multitude  of  most  ingenious  experiments  having  shown 
that  ozone  is  merely  a  peculiarly  arranged  group  of  oxygen 
atoms. 


OXYGEN. 


121 


Allotropism. 

Chemists  know  several  other  elements  capable  of  more 
than  one  modification  :  thus  sulphur  is  capable  of  at  least 
three  modifications,  possessing  three  different  sets  of  proper- 
ties ;  pure  phosphorus  is  known  in  two  separate  modifications 
possessing  different  properties  ;  the  diamond,  graphite  and 
charcoal  are  three  modifications  of  the  element  carbon. 

All  these  substances  are  designated  as  allotropic,  and  the 
abstract  property  of  chemical  elements  by  virtue  of  which 
they  are  capable  of  such  varied  forms  is  called  allotropism. 


FIG.  32.— Hydrogen  gas,  generated  by  use  of  zinc  and  sulphuric  acid,  is  then  passed 
through  a  drying  tube  containing  calcic  chloride  (CaCl2).  By  the  act  of  combustion 
the  union  of  the  dried  gas  with  oxygen  of  the  air  produces  drops  of  water. 


First  Compound  of  Oxygen  with  Hydrogen— Water. 

It  has  already  been  shown  that  the  hydrogen  escaping  from 
a  suitable  tube  may  be  lighted  in  the  nir.  If  the  burning  jet 
is  introduced  into  oxygen  gas  the  same  combustion  proceeds, 
only  with  greater  energy.  In  either  case  there  is  produced  a 
compound  of  hydrogen  and  oxygen.  This  compound  is  repre- 
sented by  the  formula  H2O,  a  formula  representing  no  other 
than  the  familiar  substance  water.  At  the  moment  of  combus- 
tion of  hydrogen  very  great  heat  is  generated.  (See  p.  65.)  In 


122 


CHEMISTRY. 


fact,  a  pound  of  hydrogen,  upon  burning  in  pure  oxygen,  yields 
about  four  times  as  much  heat  as  a  pound  of  pure  carbon 
does  in  burning  under  the  same  favorable  conditions.  Indeed, 
the  pound  of  hydrogen,  when  in  combustion,  yields  more  heat 


FIG.  33. — Apparatus  for  analysis  of  water  by  use  of  the  galvanic  battery. 

than  a  pound  of  any  other  substance  known.  On  account  of 
this  heat  the  water  resulting  from  the  burning  hydrogen  at 
first  floats  off  in  the  air  in  the  form  of  vapor ;  but  if  the 
hydrogen  flame  is  brought  in  contact  with  some  cooling  sur- 
face, the  water  formed  condenses  in  drops  upon  it,  and  thus 
it  may  be  readily  recognized  as  in  its  ordinary  form. 

A  great  multitude  of  experiments  show  that  the  composi- 
tion of  water  is  as  follows  : 


Parts  by  weight 

Parts  by  bulk. 

Atoms. 

Hydrogen 

2 

2 

2 

Oxygen  

16 

1 

1 

The  composition  of  water,  as  displayed  in  the  foregoing 
table,  has  been  demonstrated  by  analysis,  this  word  meaning 
"  the  process  of  taking  apart."  Thus  by  chemical  influences 


OXYGEN. 


123 


a  portion  of  water  may  be  subdivided  into  its  constituents 
and  their  amounts  determined.  On  the  other  hand  the  com- 
position of  water  has  also  been  made  out  by  synthesis,  this 
word  meaning  "  the  process  of  putting  things  together."  In 
this  latter  case,  by  putting  together  what  are  believed  to  be 
the  proper  proportional  amounts  of  hydrogen  and  oxygen 
to  form  water,  and  then  upon  using  some  suitable  means  for 
bringing  these  things  into  a  state  of  true  chemical  combina- 
tion, it  has  been  found  that  they  do,  in  fact,  combine  to  form 
water,  and  in  the  proportions  already  given  in  the  table. 


FIG.  34.— Apparatus  devised  by  Dumas  for  determining  the  composition  of  water. 

Second  compound  of  Oxygen  and   Hydrogen— Hy- 
drogen Dioxide. 

There  are  certain  circuitous  processes  by  which  a  com- 
pound of  oxygen  and  hydrogen,  very  different  from  water, 
may  be  produced.  This  compound  has  the  formula  H2  O2, 
and  is  called  hydrogen  dioxide.  Its  molecular  constitution 
is  represented  by  the  expression,  H — O — O— H.  It  is  a 
colorless  liquid,  somewhat  like  water,  only  thicker,  being  one 
and  a  half  times  as  heavy  as  water.  It  easily  decomposes, 
giving  up  a  single  atom  of  oxygen  in  an  active  condition. 
Curiously  enough,  the  oxygen  so  liberated  acts  at  different 
times  in  ways  that  at  first  seem  to  be  quite  contradictory  ; 
indeed  they  could  not  be  well  explained  when  the  phenome- 
na were  first  observed. 

First.  The  oxygen  so  liberated  tends  to  combine  directly 
with  many  oxides  producing  higher  oxides. 


124  CHEMISTRY. 


Second.  The  oxygen  liberated  by  hydrogen  dioxide  tends 
to  withdraw  oxygen  from  certain  other  oxides. 

The  modern  molecular  theory  of  chemical  compounds  af- 
fords an  easy  and  adequate  explanation  of  these  phenomena. 
This  theory,  as  has  already  been  pointed  out,  holds  that  the 
elementary  atoms  rarely  remain  single  :  they  prefer  the  com- 
bined form.  So,  then,  the  single  atom  of  oxygen  liberated 
from  the  molecule  of  hydrogen  dioxide  easily  attacks  certain 
substances  to  combine  with  them,  its  affinities  being  stronger 
in  its  single  condition  than  when  as  in  ordinary  oxygen  it 
exists  in  the  molecular  form  represented  by  the  symbol  O2. 
In  this  latter  form  the  affinities  of  the  two  atoms  of  oxygen 
are  partly  satisfied  by  combination  with  each  other.  On  the 
other  hand,  when  the  single  atom  of  oxygen,  liberated  by  a 
molecule  of  hydrogen  dioxide,  deoxidizes  substances,  it  does 
so  on  account  of  the  affinity  of  this  single  atom  of  oxygen  for 
another  atom  of  oxygen,  and  with  the  intent  to  form  a  more 
stable  molecule  represented  by  the  formula  O2. 

Nascent  State. 

The  oxygen  liberated  from  hydrogen  dioxide  is  called 
nascent  oxygen  (meaning  just  born,  from  the  Latin  word 
nascor,  to  be  born.) 

This  is  not  the  only  way  of  producing  nascent  oxygen,  nor 
is  oxygen  the  only  substance  that  exists  in  the  nascent  form 
characterized  by  unusually  active  powers. 

The  nascent  state  has  long  been  recognized  as  a  peculiar 
one,  and  the  molecular  theory  affords  a  satisfactory  expla- 
nation of  phenomena  before  inexplicable. 

Uses  of  Hydrogen  Dioxide. 

Hydrogen  dioxide  possesses  marked  bleaching  powers,  and 
notwithstanding  its  comparatively  high  cost  a  solution  of  it 
in  water  has  been  brought  into  commerce  and  is  used  for 
certain  delicate  bleaching  operations ;  among  these  may  be 
mentioned  the  whitening  of  the  paper  of  books  and  engrav- 
ings that  have  become  stained  or  dingy  with  age. 


OXYGEN. 


125 


The  Compound  Blowpipe. 

The  fact  that  enormous  heat  is  developed  when  hydrogen 
burns  was  known  long  ago,  and  it  gave  rise  to  the  invention 
of  a  contrivance  for  utilizing  it.  This  has  taken  the  form  of 


FIG.  .35.— Flame  of  the  oxy-hydrogen  blowpipe  directed  upon  a  crucible  in  a  furnace 
of  lime. 

the  apparatus  called  the  compound  blowpipe,  also  the  oxy- 
hydrogen  blowpipe. 

This  blowpipe,  as  usually  constructed,  has  a  single  jet  or 
tip,  to  which  there  is  conveyed  by  separate  tubes,  on  the 
one  hand  oxygen,  on  the  other  hand  hydrogen.  The  gases, 


126  CHEMISTRY. 


when  lighted,  give  rise  to  a  flame  yielding  but  little  light,  but 
of  intense  heating  power.  Many  difficultly  fusible  metals, 
such  as  iron,  for  instance,  melt  like  wax  before  it,  while  others, 
like  lead  and  zinc,  boil  and  vaporize  beneath  its  fervent 
breath.  It  must  not  be  looked  upon,  however,  as  a  mere 
chemical  toy ;  it  has  some  uses  in  the  arts.  Of  these  one  of 
the  most  prominent  is  its  application  to  the  melting  and  refin- 
ing of  the  ores  and  alloys  of  platinum,  substances  which  no 
ordinary  furnace  can  liquefy. 

For  purposes  of  this  sort  a  special  furnace  or  crucible  must 
be  provided,  and  it  must  be  constructed  of  some  substance 
that  is  itself  practically  infusible.  Such  a  material  is  found 
in  quicklime  (calcic  oxide,  CaO),  for  this  substance  does  not 
melt  under  the  influence  of  any  known  contrivance  for  pro- 
ducing heat.  Moreover  it  does  not  conduct  heat  rapidly, 
and  thus  any  heat  applied  to  the  metal  within  is  not  subject 
to  serious  loss  by  being  conducted  away  through  the  walls 
of  the  vessel.  For  melting  platinum,  then,  a  furnace  con- 
structed of  quicklime  and  having  a  cover  of  the  same  mate- 
rial, is  employed.  A  stream  of  burning  gases  from  a  com- 
pound blowpipe  is  forced  through  an  aperture  in  the  furnace- 
cover  in  such  a  way  as  to  fall  on  an  interior  crucible  contain- 
ing the  metal  to  be  melted. 

V 

The  Calcium  Light. 

Another' interesting  application  of  this  blowpipe  is  found 
in  the  lime  light,  an  appliance  also  known  as  the  calcium 
light  and  sometimes  as  the  Drummond  light.  In  this  appa- 
ratus, whatever  may  be  its  particular  form,  the  stream  of 
burning  gases  is  directed  upon  a  small  block  or  cylinder  of 
lime.  Of  course  the  block  becomes  highly  heated — in  fact, 
it  assumes  a  white  heat  without  melting;  and  while  at  this 
temperature  it  gives  out  a  dazzling  light.  This  light  has  been 
utilized  by  architects  and  engineers  for  carrying  on  impor- 
tant constructions  during  the  darkness  of  night.  It  is  also 
often  used  in  some  of  the  finer  forms  of  the  magic  lantern, 


OXYGEN.  127 


as,  for  example,  in  the  various  stereopticons  used  in  illus- 
trated lectures.  So  numerous  are  the  uses  of  the  calcium  light 
in  large  cities  that  it  has  become  a  regular  industry  there  to 
furnish  the  oxygen  and  hydrogen  gases  in  separate  iron 
cylinders  or  cans,  into  which  they  are  pumped  under  great 


FIG.  36.— Drummond  light,  or  calcium  light.    The  flame  of  the  oxy-hydrogen  blow- 
pipe directed  against  a  block  of  lime  renders  the  latter  intensely  luminous. 

pressure.  (It  is  true  that  illuminating  gas  is  sometimes 
substituted  for  hydrogen  with  decided  economy  in  cost,  and 
yet  without  serious  loss  of  illuminating  power.)  When  the 
cylinders  are  in  use  the  stop-cocks  are  slightly  opened,  and 
the  gases  are  under  sufficient  pressure  to  flow  to  the  tip  of 
the  blowpipe  as  freely  as  can  be  desired. 


128  CHEMISTRY. 


Dangerous  Explosibility   of  Mixtures   of  Oxygen 
and  Hydrogen. 

At  this  point  a  warning  should  not  be  omitted,  for  mixt- 
ures of  oxygen  and  hydrogen  gas,  whether  produced  pur- 
posely or  by  accident,  are  capable  of  very  dangerous 
explosions.  Even  a  soap-bubble,  inflated  with  the  mixed 
gases,  and  then  lighted  with  a  torch,  explodes  with  tremen- 
dous violence  and  a  loud  report.  This  result  is  all  the  more 
wonderful  when  the  extreme  thinness  and  weakness  of  the 
filmy  confining  envelope  are  considered.  Such  explosions  are 
in  entire  harmony  with  the  various  statements  already  made. 
For  when  the  two  gases  combine,  the  intense  heat  gen- 
erated gives  rise  to  a  momentary  but  enormous  expansion 
of  the  vapor  of  water  produced  by  the  combustion.  The 
greatly  expanded  vapor  strikes  the  air  a  sharp  and  violent 
blow.  In  another  instant,  however,  the  vapor  suddenly  cools 
and  condenses  to  an  exceedingly  minute  drop  of  liquid  water; 
the  air  that  was  previously  forced  outward  immediately  falls 
into  the  vacancy  left,  and  now  a  second  blow  results.  It  is 
these  two  violent  shocks,  the  one  following  the  other  in 
almost  instantaneous  succession,  that  produce  the  report ; 
and  to  the  same  causes  must  be  referred  the  terribly  de- 
structive results  of  the  accidental  explosion  of  considerable 
quantities  of  the  mixed  gases.  It  is  plain,  therefore,  that  all 
contrivances  destined  to  employ  these  gases  in  close  prox- 
imity must  be  used  with  great  caution. 

Oxygen  as  Related  to  Combustions  in  General. 

But  oxygen  is  prominent  in  many  other  combustions  be- 
sides that  of  hydrogen.  Of  course  the  best  known  and  most 
common  are  those  in  which  the  ordinary  forms  of  fuel  are 
the  things  burned.  Here  generally  the  principal  constituent 
of  the  combustible  material  is  carbon. 

Oxygen  as  Related  to  Animal  Respiration. 

Oxygen  performs  also  one  of  its  most  important  offices  in 
connection  with  the  process  of  animal  respiration.  In  the 


OXYGEN.  129 


fulfillment  of  this  mission  no  element  is  known  that  can  in 
any  way  act  as  a  substitute.  The  gas  which  is  to  serve  as 
the  breath  of  life  for  the  humblest  as  well  as  the  most 
exalted  individuals  of  the  animal  creation  must  possess  a 
combination  of  qualities  truly  marvelous  when  residing  in  a 
single  substance.  Even  a  brief  description  of  the  ways  in 
which  it  discharges  this  delicate  and  manifold  duty  ought  to 
substantiate  the  general  proposition. 

Oxygen  is  qualified  to  sustain  respiration  by  virtue  of  the 
exceeding  abundance  of  the  atmospheric  air;  an  abundance 
such  that  it  extends  above  our  heads  a  distance  of  forty 
thousand  times  the  height  of  a  man.  Nor  are  the  denizens 
of  the  sea  forgotten,  for  oxygen  possesses  such  capacity  for 
dissolving  in  water  that  there  exists,  absorbed  in  the  liquid 
of  the  rivers  and  oceans,  enough  of  this  vital  gas  to  furnish 
breath  for  all  the  finny  tribes. 

Again,  the  oxygen,  so  violent  in  its  combinations,  is  yet 
bland  enough  to  pass  through  all  the  delicate  passages  lead- 
ing into  the  lungs  without  exciting  the  throat  to  the  slight- 
est cough;  to  filter  through  the  fine  membranes  of  the  lungs 
without  doing  an  injury;  to  saturate  the  blood,  and  to  flow 
to  every  tissue  and  cell  of  the  body,  and  not  only  do  no 
harm  but  every-where  accomplish  a  reviving  work.  It  per- 
forms throughout  the  animal  frame  a  well-regulated  but  no 
inconsiderable  combustion.  Indeed  the  body  of  a  living 
animal  may  be  properly  looked  upon  as  a  kind  of  furnace, 
taking  in  air  whose  oxygen  shall  sustain  the  combustion  of 
worn-out  parts.  Nay,  more;  these  as  they  burn  do  in  their 
very  death  aiford  as  their  final  contribution  that  warmth  and 
glow  which  maintains  the  animal  temperature  at  the  vital  point. 

While  carrying  out  the  important  functions  just  referred 
to,  oxygen  produces  several  gaseous  substances,  each  of 
which,  as  if  under  the  constant  direction  of  an  ever-watchful 
barometer,  maintains  its  proper  bulk  and  pressure,  so  as  to 
do  no  injury  to  the  most  delicate  capillary  of  a  vein  or  to 
the  tender  walls  of  the  smallest  chambered  cell  of  the  lungs. 
With  each  breath  exhaled  from  the  *  system,  the  blood,  and 
9 


CHEMISTRY. 


thence  the  lungs,  discharge  the  gaseous  products  of  the  com- 
bustion already  described;  plainly  they  do  it  somewhat  in 
the  same  manner  as  a  chimney  does  in  its  proper  action,  only 
the  lungs  do  their  work  in  a  far  more  perfect  way. 

The  parallelism  is  not  strained  here,  for  the  burning  of 
the  animal  tissue  in  the  body  gives  rise  principally  to  the 
production  of  the  gas  called  carbon  dioxide  and  the  vapor  of 
water,  just  as  when  a  fagot  burns  in  the  chimney-place  the 
carbon  and  the  hydrogen  of  the  wood  oxidize  into  the  self- 
same products,  both  of  which  are  wafted  up  the  flue  and  out 
into  the  great  ocean  of  atmosphere  beyond. 


READING  REFERENCES. 

Gases,  Liquefaction  of. 

Cailletet,  L. — Aunales  de  Cliiraie  et  de  Physique.     5  Ser.    xv,  132. 

Chera.  News,     xxxvii,  11. 

Cailletet,  L. — Science,     vi,  21. 

Coleraan,  J.  J. — Chem.  News,     xxxix,  87. 

Pictet,  R. — Annales  de  Chimie  et  de  Physique.     5  Ser.  xiii,  145. 

Chem.  News,     xxxvii,  1,  23,  83. 

Roscoe  and  Schorlemmer. — Chemistry.     New  York.     1878.     ii,  pt.  II, 
516. 

Schutzenberger,  P.— Traite  de  Chimie  Geuerale.     i,  25. 
Priestley,  Joseph. 

Brougham,  H. — Lives  of  Men  of  Letter?,  etc.     p.  402. 

Amer.  Chemist,     iv,  362-441 ;  v,  11-35.  43,  210. 

Ozone  or  Active  Oxygen. 

Roscoe  and  Schorlemmer, — A  Treatise  on  Chemistry,  i.  194. 


WATER.  131 


XVI. 

WATER. 

IS  the  most  prominent  compound  of  oxygen,  water 
may  properly  receive  the  reader's  attention  at 
this  time. 

He  who  stands  upon  a  high  cliff  and  looks  out 
upon  the  ocean,  experiences  as  one  of  his  strongest  impres- 
sions, that  of  the  boundlessness  of  the  expanse.  And  it  is 
true  that  the  area  of  terrestrial  waters  is  very  wide,  for  in 
the  aggregate  their  waves  cover  more  than  three  fourths  of 
the  earth's  surface.  But  while  their  superficial  extent  is  so 
great,  their  depths  are  relatively  but  small.  When  compared 
with  the  diameter  of  the  earth  the  deepest  ocean  seems  shallow 
indeed.  If  the  waters  of  the  oceans  were  dried  up,  or  other- 
wise wiped  away,  the  roughness  of  the  dry  globe  would  be 
less  relatively  than  the  roughness  of  an  orange.  In  fact  the 
total  amount  of  water  actually  existing  upon  the  earth's  sur- 
face is  less — relatively  to  the  entire  mass  of  the  globe — than 
the  amount  that  would  remain  on  an  orange  after  dipping  it 
into  a  basin  of  water  and  then  withdrawing  it.  Notwith- 
standing these  facts,  the  amount  of  water  is  so  vast  in  pro- 
portion to  the  littleness  of  human  beings,  and  it  has  taken 
so  prominent  a  part  in  the  phenomena  observable  by  man, 
and  it  has  been  such  a  powerful  agent  in  the  geological  eras 
of  the  past,  that  it  is  not  surprising  that  its  properties  and 
history  have  excited  the  interest  of  students  and  thinkers  of 
all  times.  In  the  light  of  modern  chemical  knowledge,  too, 
its  various  offices  create  an  admiration  that  is  heightened 
the  more  they  are  considered. 

The  chemical  constitution,  the  characteristics,  the  proper- 
ties, and  the  uses  of  water,  are  important  chemical  topics ; 
when  one  considers,  further,  the  varied  forms  and  uses  in 
which  this  familiar  substance  is  employed  in  nature  and  in 


132 


CHEMISTRY. 


the  arts,  a  subject  is  suggested  that  might  well  furnish 
material  for  a  volume.  Plainly,  then,  only  a  few  of  its  more 
striking  adaptations  can  be  discussed  here. 


Importance  of  Water  to  Living  Beings. 

To  living  animals  and  plants  water  nppears  to  be  abso- 
lutely indispensable.     The  reason  for  this  is  found  not  only 

in  tlie  fact  thnt  water 
forms  a  necessary  constit- 
uent part  of  most  living 
beings,  but  also  because 
it  serves  as  a  sort  of 
vehicle  by  virtue  of 
whose  properties  the  vital 
processes  are  conducted 
and  through  which  the 
vital  currents  flow.  It  is 
easy  to  understand  that 
if  the  atmospheric  air, 
which  lies  wrapped  about 
our  globe  like  a  thin  veil 
were  suddenly  wafted 
away,  animal  life  would 
be  instantly  extinguished.  Now  water  is  not  less  essential 
than  air.  Banish  water  from  the  earth,  and  the  life  of  all 
animal  and  vegetable  beings  would  instantly  take  its  flight. 
For  the  blood,  that  living  tide  which  courses  through  the 
natural  gates  and  alleys  of  the  body,  contains  water  to  the 
extent  of  nearly  80  per  cent,  of  its  weight.  Again,  pure, 
unadulterated  milk,  rich  as  it  is  in  solid  food  materials  dis- 
solved or  suspended  within  it,  contains  not  far  short  of  90 
per  cent,  of  water.  And  further,  an  examination  of  vegeta- 
ble products  reveals  in  them  a  preponderance  of  water  such 
as  would  not  at  first  be  suspected.  Thus  the  following 
brief  table  represents  facts  so  surprising  that  it  is  at  first 
difficult  to  accept  them; 


FIG.  37.— Egyptian  Water-carrier. 


WATER. 


Apples  contain  about  80  per  cent,  of  water. 
Turnips  contain  about  90  per  cent,  of  water. 
Cucumbers  contain  about  97  per  cent,  of  water. 

Finally,  as  an  extreme  example  among  the  kingdoms  of 
life,  it  may  be  mentioned  that  some  forms  of  jelly-fish,  as 
taken  from  their  appropriate  home  in  the  ocean,  have  been 
found  to  contain  not  less  than  99  9-10  per  cent,  of  water.* 

The  extraordinary  and  indeed  incredible  proportion  of 
water  in  living  beings  is  associated  with  the  numerous, 
varied,  and  even  apparently  contradictory  offices  to  be  per- 
formed by  it,  and  the  fitness  of  water  to  fulfill  these 
requirements  is  referable  further  to  the  curious  and  interest- 
ing properties  with  which  it  is  endowed.  But  it  is  so 
familiar  to  every  one,  and  so  bland  in  its  action  in  its  rela- 
tion to  most  well-known  substances,  that  the  ordinary 
observer  fails  to  recognize  these  properties  and  their  marvel- 
ous adaptations. 

One  of  the  properties  most  appropriate  for  presentation 
in  this  connection  is  the  power  water  possesses  of  dissolving 
gases.  It  is  capable  of  storing  up  within  itself,  concealed 
from  human  view,  almost  every  gas  with  which  it  comes  in 
contact.  It  displays  this  power  upon  (he  atmospheric  air, 
not  only  in  its  better  known  relations  to  man  and  the  higher 
animals,  but  also  as  respects  the  humbler  population  of  the 
globe.  It  will  be  seen  by  and  by  that  the  air  consists  in  the 
main  of  a  mixture  of  two  gases  very  different  in  their 
properties.  One  is  oxygen,  the  sustainer  of  animal  respira- 
tion ;  the  other,  nitrogen,  the  inactive  substance  existing  in 
the  air  as  a  mere  diluent  of  the  active  oxygen.  Xow  water 
possesses  a  very  curious  relation  to  these  gases;  it  dissolves 
a  larger  proportion  of  oxygen  than  of  nitrogen.  By  reason 
of  this  property  it  acts  upon  the  atmospheric  air  with  a 
selective  effect  highly  suggestive  of  intelligent  plan.  For 
the  gas  it  selects  to  dissolve  in  larger  proportional  quantity 
is  oxygen — the  one  absolutely  needed  to  take  the  principal 

*  COOKE,  JOSIAH  P. :  Religion  and  Chemistry.    New  York,  1864.   p.  148. 


134 


CHEMISTKY. 


part  in  supporting  the  respiration  of  the  countless  millions 
of  fishes  that  make  their  natural  homes  in  all  great  bodies  of 
water. 

Terrestrial  Circulation  of  Water. 

Water  is  the  chief  liquid  of  our  great  globe.  And  it  car- 
ries on  here  a  continued  and  beneficent  double  circulation 
which  may  be  properly  likened  to  that  of  the  living  animal  and 
plant,  except  that  it  proceeds  on  the  cosmical  scale.  The  one 
portion  of  this  circulation  may  be  described  as  starting  in  the 
depths  of  the  ocean ;  thence  permanent  currents  continually 

flow  in  certain 
definite  direc- 
tions and  ulti- 
mately regain 
their  starting- 
place.  These 
currents  c  o  n- 
tribute  to  make 
the  seas  the 
highways  of  na- 
vies even  more 
c  omple  t  ely 

than  they  would  be  if  the  waters  were  always  at  rest.  A  yet 
more  striking  circulatory  movement  is  that  initiated  by  the 
volumes  of  moisture  which  rise  by  constant  evaporation  from 
the  temperate  as  well  as  the  tropical  seas.  This  water, 
ascending  into  the  higher  atmosphere,  is  carried  by  currents 
of  the  air  hither  and  thither  and  over  the  land,  where  by 
mountain  ranges,  or  other  natural  means  adequate  to  this 
purpose,  it  becomes  precipitated  into  a  solid  or  liquid  form. 
In  this  condensed  form  it  is  recognized  as  beneficent  when 
it  is  in  cloud  masses,  which  delight  mankind  with  the  purity 
of  their  fleecy  whiteness  or  the  beauty  of  their  gorgeous 
coloring,  as  well  as  when  it  is  in  the  form  of  showers  which 
refresh  the  thirsty  earth,  or  as  the  snow  which  protects  it. 
The  rain  and  snow  supply  the  numberless  rivulets  that  contrib- 


FIG.  38. — Water  in  the  form  of  cumulus  clouds. 


WATER.  1S5 


ute  to  make  up  rivers,  and  these  flow  joyfully  to  the  ocean 
and,  mingling  in  its  waters,  return  to  the  source  from  which 
they  came.  Thus  has  been  pictured  in  brief  an  outline  of 
the  circulation  previously  suggested. 

Water  in  the  Solid  Form. 

Again,  certain  properties  of  water  other  than  these 
already  stated  are  worthy  of  presentation.  Perhaps  it  is  not 
inconsistent  with  the  truth  to  say  that  they  are  even  more 
plainly  beneficial.  Thus,  in  the  form  of  snow,  water  appears 
at  first  sight  to  be  an  emblem  of  cold.  But  when  it  falls 
upon  the  earth  it  becomes  a  mantle  or  coverlet,  which  pro- 
tects the  soil  from  the  chilling  effects  of  the  wintry  season 
and  from  that  rapid  loss  of  heat  by  radiation  off  into  space 
which  the  fields  would  suffer  without  this  protective  coating. 
And  so  ice,  as  it  forms  on  the  surface  of  lakes  and  ponds, 
manifests  several  remarkable  properties.  Of  these  only  two 
will  be  discussed  here.  They  are  both  due  to  its  power 
of  expanding  at  the  moment  of  solidification.  Most  per- 
sons make  acquaintance  with  this  characteristic  of  water  by 
the  inconvenient  bursting  of  pitchers  and  pipes,  recognized 
as  a  disagreeable  attendant  upon  the  winter's  cold.  When 
looked  upon  with  more  fully  instructed  eyes,  however,  it  is 
discovered  to  be  one  feature  of  a  remarkable  system  which 
results  in  great  benefit  to  the  inhabitants  of  the  earth.  For 
it  is  plain  that  as  water  in  freezing  expands,  it  thereby 
becomes  relatively  lighter.  On  this  account  ice  floats  in 
water,  whereas  solid  substances  generally  sink  in  liquid  mat- 
ters -of  their  own  kind.  Now  the  ice  formed  upon  lakes  in 
the  winter  stays  at  the  top,  and  thus  protects  the  water 
below  from  the  chill  of  the  colder  air;  so  it  prevents  the 
lakes  from  becoming  uninhabitable  to  the  fish.  The  same 
property  prevents  a  lake  from  becoming  a  mass  of  solid 
from  the  bottom  upward,  as  would  be  the  case  if  the  ice, 
upon  freezing,  went  to  the  bottom.  The  summer's  sun 
would  hardly  be  capable  of  thawing  the  solid  masses  so 


136  CHEMISTRY. 


formed.  This  same  curious  fact — the  expansion  of  ice  at 
the  moment  of  its  formation — contributes  to  the  fertility  of 
the  soil.  Thus  the  water  that  penetrates  the  crevices  of 
rocks  expands  upon  freezing,  chipping  off  those  rocks,  in 
fact  pulverizing  them  little  by  little,  and  so  conveying  fresh 
and  valuable  materials  to  the  earth's  soils. 

Water  as  Affecting  Climate. 

Further,  the  relations  of  water  to  heat  are  very  interest- 
ing. "  The  general  aqueous  circulation  of  the  earth  is  a 
great  steam-heating  apparatus,  with  its  boiler  in  the  tropics 
and  its  condensers  all  over  the  globe.  The  sun's  rays  make 
the  steam.  And  wherever  dew,  rain  or  snow  forms,  there 
heat,  which  came  originally  from  the  sun,  and  which  has 
been  brought  from  the  tropics  concealed  in  the  folds  of  the 
vapor  in  the  form  of  latent  heat,  is  set  free  to  warm  the 
less  favored  regions  of  the  earth.  [Latent  heat  is  heat  either 
concealed  or  else  suddenly  made  manifest  at  the  moment 
of  change  of  a  substance  from  one  of  the  three  states  of 
matter,  solid,  liquid,  or  gaseous,  to  another.]  This  apparatus 
in  nature,  although  so  much  simpler  and  working  without 
pipes,  iron  boiler,  or  radiator,  is  exactly  the  same  in  princi- 
ple as  the  steam  heaters  "  which  may  be  seen  at  work  in 
many  large  buildings.*  In  other  words,  when  water  is 
changed  into  vapor  in  the  tropics,  heat  is  not  only  requisite 
to  the  operation,  but  a  definite  quantity  of  heat  is  actually 
stored  up  within  the  vapor  so  produced.  On  the  other 
hand,  whenever  in  some  cooler  parts  of  the  globe  this  same 
portion  of  vapor  condenses  into  the  form  of  liquid,  that 
heat  that  was  stored  within  it  at  the  tropics  is  immediately 
evolved,  and  contributes  materially  to  the  warmth  of  the 
region  where  condensation  takes  place.  Nay,  more;  if  the 
water,  instead  of  falling  as  rain,  falls  as  snow  a  still  larger 
amount  of  heat  is  by  this  means  given  out  into  the  atmos- 
phere. This  last  statement  is  insensibly  substantiated  by 

*COOKE,  JOSIAH  P. :  Religion  and  Chemistry.    New  York,  1884.    p.  135. 


WATER.  18? 


the  expression  often  heard  in  winter,  "the  weather  is  too 
cold  for  snow."  This  common  expression,  translated  into 
scientific  language  means,  "  if  snow  were  already  condensing 
in  the  upper  air,  and  ready  to  fall,  the  heat  given  out  by  it 
would  have  reached  us  in  advance." 

It  is  not  only  with  respect  to  those  changes  taking  place 
when  the  vapor  of  water  changes  to  the  liquid  or  the  solid 
form  that  its  heat  relations  are  beneficial  to  mankind.  No 
lake  can  change  one  degree  in  temperature — that  is,  grow 
warmer  or  cooler — without  at  the  same  time  exercising  a 
contrarywise  influence  upon  the  air  about  it,  and  thus  a 
regulating  one. 

This  is  by  virtue  of  that  property  of  water  called  its  spe- 
cific heat.  (Specific  heat  is  the  relative  amount  of  heat 
concealed  or  else  liberated  when  a  body  undergoes  a  change 
of  temp-erature.) 

In  explanation  of  this  declaration  the  following  state- 
ments may  be  made:  When,  in  the  intensely  hot  days  of 
summer,  a  lake  or  any  mass  of  water  becomes  influenced  by 
the  high  temperature,  of  course  its  waters  become  warmer. 
But  it  is  a  curious  fact  that  it  takes  more  heat  to  raise  the  tem- 
perature of  water  one  degree  than  it  does  to  raise  the  tem- 
perature of  the  adjoining  land  one  degree — or  in  fact  to  raise 
any  other  substance  known  one  degree.  Thus  it  appears 
that  a  given  amount  of  heat  applied  in  a  summer  day  to  a 
lake  will  be  absorbed  within  the  waters  of  that  lake  without 
raising  the  temperature  of  those  waters  to  the  extent  that 
might  be  expected.  So,  then,  in  hot  weather  the  lake 
becomes  an  equalizer  of  temperature  with  a  tendency  in  the 
opposite  direction,  that  is  to  cool  the  air  about  it.  Now  in 
cold  weather  it  becomes  equally  beneficial,  only,  as  might  be 
expected,  in  the  opposite  direction.  Thus  the  store  of  heat 
retained  by  the  liquid  water  is  given  out  as  the  lake  cools. 
For  just  as  the  water  in  order  to  rise  one  degree  in  tempera- 
ture requires,  and  indeed,  absorbs  more  heat  than  any  other 
substance  known,  so  naturally  the  same  water,  in  cooling 
one  degree  in  temperature,  freely  gives  out  the  amount  of 


138  CHEMISTRY. 


heat  it  had  previously  stored  within  itself,  which,  as  has  been 
said,  is  greater  than  that  stored  up  by  any  other  substance 
known. 

The  remarks  thus  far  made  on  water  as  influencing  cli- 
mate relate  to  it  chiefly  when  in  the  liquid  form,  and  in 
considerable  bodies  on  the  surface  of  the  earth. 

The  atmosphere  above  our  heads  contains  large  quantities 
of  water  in  the  aggregate. 

This  water  is  in  the  form  of  vapor,  it  is  true,  but  notwith- 
standing this  condition  it  is  capable  of  exerting  a  marked 
and  important  effect  on  climate,  retaining  the  heat  of  the 
sun  in  a  manner  more  fully  described  in  a  later  chapter. 
(See  page  180,  and  also  reading  reference  on  page  183.) 

Water  as  a  Working  Contrivance. 

When  the  moisture  of  the  tropical  ocean  is  taken  up  into 
the  air  by  evaporation,  the  sun  has  thereby  done  a  truly  stu- 
pendous amount  of  work.  For  has  it  not  lifted  up  high  into 
the  atmosphere  an  enormous  weight  of  this  liquid  material  ? 
Now  as  the  vapor  is  wafted  over  the  land  preparatory  to 
falling  as  rain,  it  has  acquired  a  position  in  which  it  may  do 
a  great  amount  of  work  for  human  uses  ;  for  every  rain 
drop,  falling  from  its  lofty  position  in  the  air,  acquires 
thereby  a  momentum  which  represents  a  quantity  of  force, 
minute  in  each  individual  case,  but  truly  vast  in  the 
aggregate.  Of  this  sum  total  but  a  small  portion  is 
employed  for  man's  industrial  uses  ;  only  a  minute  frac- 
tional part  is  harnessed  to  the  wheels  that  grind  his  food 
or  weave  his  clothing  or  transform  the  trees  of  the  forest 
into  his  habitations  ;  yet  the  amount  he  does  so  employ — 
compelling  it  to  do  his  work  for  him — represents  an  enor- 
mous total  quantity.  All  this  work  done,  as  well  as  all  that 
might  be  done  by  the  vast  quantities  of  water  allowed  to 
escape  and  violently  run  to  waste,  is  referable  back  again  to 
the  sun  of  the  tropics,  which  has  been  enabled,  by  reason 
of  the  wonderful  properties  of  water,  to  store  up  all  this 
power  within  it. 


WATER.  130 


In  view  of  what  has  been  said,  the  sun  and  water  of  the 
tropics  may  be  compared  not  inappropriately  to  the  chief 
artificial  contrivances  used  in  modern  times  for  generating 
and  applying  mechanical  power — boiler  and  engine.  As  an 
ordinary  steam-boiler  imparts  to  water  the  expansive  and 
working  power  of  steam,  and  again  the  ordinary  steam- 
engine  utilizes  this  steam  power  so  that  it  may  be  directly 
applied  to  the  labor  of  man's  workshops,  so  the  sun  of  the 
tropics  lifts  the  water  of  the  ocean  high  up  into  the  air,  and 
thus  may  be  likened  to  the  boiler ;  while  the  rapidly  run- 
ning brooks  may  fitly  represent  an  engine  in  motion,  ready 
to  actuate  any  machine  to  which  by  proper  appliances  it 
may  be  attached. 

Kinds  of  Water. 

The  kinds  of  water  found  in  nature  differ  chiefly  in  the 
foreign  matters  they  contain.  These  matters  differ  very 
much  in  their  character.  Some  are  merely  suspended,  floating 
in  the  water;  others  are  invisible,  fully  dissolved.  They  differ 
also  in  their  chemical  nature,  as  is  evidenced  by  the  different 
remedial  substances  existing  in  mineral  spring-waters  of 
different  places. 

Reference  has  already  been  made  to  the  well-established 
fact  that  most  of  the  water  of  our  globe  is  all  the  time  mov- 
ing onward  in  what  may  be  called  a  natural  circuit.  Now 
the  character  of  any  given  natural  water  is  dependent  mainly 
upon  the  part  of  the  natural  circuit  at  which  the  sample  of 
water  under  consideration  is  arrested. 

The  circulation  thus  referred  to  may  be  briefly  represented 
in  four  stages. 

The  first  stage  is  that  in  which  the  water  is  rising  as  vapor 
in  the  atmosphere. 

The  second  stage  is  that  in  which  the  water  is  falling  to 
the  earth  in  rain. 

The  third  stage  is  that  in  which  the  water  flows  down- 
ward over  the  land  in  brooks  and  rivers. 


140  CHEMISTRY. 


The  fourth  stage  is  that  in  which  the  water  rests  in  the 
hollow  places  of  the  globe,  as  the  great  oceans. 

Of  course  it  is  easily  seen  that  this  circuit  is  ever  repeated, 
the  evaporation  taking  place  at  the  surface  of  the  sea  being 
the  greatest  source  of  moisture  in  the  atmosphere. 

But  while  most  of  the  moisture  evaporated  from  the  ocean 
and  condensed  as  rain  returns  by  the  rivers  to  the  great  oceans, 
a  part  of  it  is  diverted — where  the  surface  configuration  of 
the  earth  gives  rise  to 'small  hollows  not  connected  with  the 
oceans — and  salt  lakes  are  thus  formed.  They  are  virtually 
little  oceans. 

Again,  in  some  cases,  falling  rain,  instead  of  proceeding 
directly  toward  the  ocean,  strikes  upon  portions  of  the  earth 
having  considerable  porosity,  and  then  it  sinks  below  the 
surface  and  takes  such  subterranean  course  as  the  strata  it 
meets  dictate.  In  this  latter  case,  however,  the  subterranean 
waters  often  come  to  the  surface  again  through  natural  fis- 
sures, as  in  the  case  of  mineral  springs,  or  by  artificial  open- 
ings, as  in  the  case  of  wells. 

There  has  thus  far  been  briefly  indicated  in  their  relations 
to  each  other,  and  as  parts  of  the  natural  circulation,  rain- 
water, brook  or  river-water,  sea-water  or  water  of  salt  lakes, 
and  again,  as  a  sort  of  side  branch  from  the  main  chief  current, 
mineral  spring-water  and  well-water. 

Rain-water.  Rain-water,  when  it  first  condenses  in  the 
higher  atmosphere,  must  be  regarded  as  perfectly  pure  water. 
In  falling  toward  the  earth,  however,  it  dissolves,  from  the 
gases  of  the  atmosphere,  some  oxygen,  some  nitrogen,  some 
carbon  dioxide,  some  ammonia  gas.  After  thunder-storms 
it  also  takes  from  the  air  some  ammonic  nitrate  (NII4NO3) 
a  substance  believed  to  be  produced  by  the  influence  of  the 
electric  discharge  upon  the  elementary  gases  always  present 
in  our  atmosphere. 

Of  course  in  the  vicinity  of  large  cities,  especially  those  con- 
taining many  manufacturing  establishments,  rain-water  col- 
lects many  other  substances.  The  air  of  towns  imparts  to 
the  rain-water  spot,  and  dust,  and  ashes,  and  even  sulphuric 


WATER,  141 


acid,  from  the  coal  burned.  To  these  must  be  added,  of 
course,  all  those  special  impurities  cast  out  by  the  chimneys 
of  special  manufacturing  establishments,  and  there  must  still 
be  added  large  quantities  of  organic  refuse,  cast  forth  from 
living  animals — and  dead  as  well — representing  in  the  aggre- 
gate no  trifling  amount  of  organic  contamination. 

All  this  has  reference,  of  course,  to  rain-water  that  has  been 
carefully  collected.  Rain-water,  as  ordinarily  collected  from 
the  roofs  of  a  city, is  often  contaminated  from  the  materials 
of  the  roofs  as  well  as  by  the  dust  collected  upon  them. 

While,  therefore,  the  rain-water  carefully  collected  in  the 
open  country  may  be  comparatively  pure,  rain-water  col- 
lected in  the  city  may  be  quite  otherwise. 

River-water.  Rivers  derive  their  chief  supply  of  water  from 
direct  surface  drainage.  To  this  there  is  sometimes  added 
water  that  has  taken  a  short  underground  course  and  feeds 
the  river  through  the  agency  of  springs. 

Ordinary  river  waters  in  their  natural  conditions  are  com- 
paratively pure.  Whatever  impurities  are  in  them  depend 
mainly  upon  the  character  of  the  water-shed.  Some  granitic 
rocks  allow  the  river-waters  flowing  over  them  to  come  away 
practically  unaffected;  again,  some  sandy  soils  not  only  them- 
selves impart  but  little  impurity,  they  sometimes  act  as  filters 
of  the  water  passing  through  them,  removing  from  it  impuri- 
ties originally  contained  in  it. 

While  water  of  thinly-settled  regions  derives  relatively 
few  impurities,  that  of  densely  populated  places  often  receives 
from  farms  and  human  habitations  and  factories  vast  amounts 
of  foreign  matters,  most  of  them  properly  considered  as  pol- 
luting. 

Sea-water  and  water  of  salt  lakes.  The  accumulation  of  salts 
in  the  oceans  and  in  the  salt  lakes  is  largely  due  to  the  fact 
that,  while  the  rivers  flowing  into  them  are  continually  carry- 
ing mineral  matters  toward  them,  the  water  evaporating 
from  them  is  practically  pure.  Of  course  the  sea-water  of 
different  localities  might  be  expected  to  contain  matters  of 
slightly  varying  quality  because  of  differences  in  the  terres- 


142  CHEMISTRY. 


trial  strata  furnishing  them.  They  might  also  be  expected 
to  vary  in  quantity  because  of  differences  in  the  amount  of 
evaporation  compared  with  the  flow  of  river-waters  toward 
them,  and  also  because  of  the  varying  influences  of  oceanic 
currents.  Thus  the  water  of  the  Mediterranean  has  about 
one  tenth  more  mineral  matter  than  the  waters  of  larger 
oceans — a  fact  which  is  due  partly  to  the  great  amount  of 
evaporation,  referable  to  the  hot  winds  from  the  Great  Desert, 
and  also  to  the  limitations  upon  its  circulation,  referable  to 
the  narrow  and  comparatively  shallow  passage  at  Gibraltar. 

The  average  composition  of  sea- water  may  be   stated  as 
follows : 


PER   CENT. 

Calcic  carbonate  (CaC03) 003 

Magnesic  bromide  (MgBr2).. .       .002 
Other  matters  aggregating. . .       .025 


Water 96.470 

Sodic  chloride  (NaCl) 2.700 

Potassic  chloride  (KC1) 070 

Magnesic  chloride  (MgCla),  . .       .360 

Magnesic  sulphate  (MgS04). .       .230  100.000 

Calcic   sulphate  (CaS04) .140 

Spring-water.  The  water  of  mineral  springs  differs  from 
ordinary  well-water  in  that  while  it  contains  usually  very 
small  amounts  of  organic  matters — that  is,  animal  and  vege- 
table matters — it  often  contains  very  large  amounts  of  min- 
eral matters. 

It  is  also  generally  charged  with  gases.  The  most  com- 
mon gas  thus  present  is  carbon  dioxide,  but  some  spring- 
waters  contain  oxygen,  nitrogen,  sulphuretted  hydrogen  and 
hydrocarbons. 

The  large  amount  of  mineral  matters  present  in  true  min- 
eral waters  is  due  partly  to  the  fact  that  the  waters  have 
filtered  to  great  depths  in  the  earth  and  have  come  in  con- 
tact with  considerable  deposits  of  mineral  matter,  and  this 
too,  with  the  water  under  so  great  pressure  as  to  favor  solv- 
ent action. 

Again,  some  of  the  gases,  notably  carbon  dioxide,  held  by 
mineral  waters  increase  very  largely  the  solvent  power  of  the 
water.  The  spring- waters  of  the  civilized  world  vary  very 
much  in  their  remedial  influences  because  the  substances  con- 


WATER.  143 


tained  by  the  waters  vary  very  much.  Partly  on  this  ac- 
count classification  of  them  is  difficult;  they  are  capable, 
however,  in  a  general  way,  of  being  classified  according  to 
the  acid  radicles  predominating,  &s,  first,  carbonated;  second, 
sulphuretted  and  sulphatic  ;  third,  chlorinated  ;  fourth,  sil- 
icious. 

Again,  they  may  be  classified  according  to  the  metallic 
radicles  prevailing  in  them,  as,  first,  alkaline  ;  second,  magne- 
sian  ;  third,  calcareous  ;  fourth,  chalybeate  (when  containing 
iron  in  abundance).  A  given  water  may,  perhaps,  be  classed 
under  both  groups  at  once ;  thus  it  might  be  said  to  be  at 
once  carbonated  and  alkaline. 

Well-water.  Well-waters  have  already  been  classified  as 
belonging  to  the  same  group  as  mineral  spring-waters.  The 
well-waters,  however,  pass  through  a  smaller  quantity  of 
earth  and  so  take  up  less  mineral  matter. 

When  wells  are  situated  in  populous  districts  their  waters 
often  become  directly  or  indirectly  impregnated  with  danger- 
ous impurities,  such  as  animal  and  vegetable  matters  which 
have  drained  into  them  from  cesspools  or  sewers. 

If  such  waters  are  used  for  drinking  or  cooking  they  are 
often  extremely  dangerous  ;  many  epidemics  of  certain  classes 
of  diseases,  such  as  typhoid  fever  and  cholera,  are  directly 
traceable  to  the  domestic  use  of  water  contaminated  by  sew- 
age. 

Deep  wells,  called  in  general  artesian  wells,  have  sometimes 
yielded  waters  resembling  mineral  spring-water.  Sometimes, 
however,  such  water  has  been  found  comparatively  free  from 
mineral  matter,  and,  indeed,  from  organic  matter,  so  as  to  be 
well  fitted  for  drinking  and  cooking  purposes.  It  seems,  in 
fact,  as  if  the  water  had  undergone  an  entirely  succcessful 
natural  process  of  filtration. 


144  CHEMISTRY. 


XVII. 

SULPHUR. 

jULPHUK,  in  its  aggregate  in  the  earth,  is  by  no 
means  an  abundant  element.  Thus,  its  quantity 
is  far  inferior  to  that  of  oxygen,  as  is  strikingly 
illustrated  by  the  diagram  already  presented. 
(See  page  17.)  Yet  sulphur  was  recognized  by  human  be- 
ings thousands  of  years  before  oxygen,  which  it  has  already 
been  stated  was  discovered  in  1774.  The  comparative  late- 
ness of  the  discovery  of  this  latter  element,  now  known  to  be 
that  one  which  predominates  largely  over  all  others  in  the 
earth,  is  due  partly  to  the  fact  that  free  oxygen  almost  in- 
variably exists  in  gaseous  form,  and  that  the  idea,  or  notion, 
of  gas  is  one  of  recent  growth.  The  fact  that  sulphur  was 
recognized  so  much  earlier  is  due  to  many  circumstances. 
First.  It  is  found  in  the  earth  in  the  solid  condition — a 
form  at  once  tangible  and  easy  of  recognition.  Second.  Its 
yellow  color  helps  to  render  it  noticeable.  Third.  It  exists 
in  the  earth  in  countries  which  have  long  been  the  abode  of 
civilized  beings.  Thus  it  was  early  recognized  in  Italy. 
Fourth.  It  occurs  in  deposits  of  such  a  character  that  it  can 
be  readily  obtained  in  a  comparatively  pure  form  from  them. 
Fifth.  It  possesses  remarkable  properties  some  of  which 
would  be  easily  detected  even  by  savage  peoples,  while 
others  have  for  centuries  excited  great  interest  in  the  minds 
of  students  of  alchemy  and  chemistry.  One  of  those  prop- 
erties is  the  ease  with  which  it  assumes  a  liquid  form — that 
is,  melts — when  slightly  heated.  Another  is  the  readiness 
with  which  it  takes  fire  and  burns  in  the  air.  A  third, 
closely  connected  with  the  foregoing,  is  the  striking  blue 
flame  produced  when  it  burns.  Still  another,  and  not  less 
noticeable  one,  is  the  choking  and  disagreeable  odor  attend- 
ant upon  this  combustion. 


PLATE  VI.— Sketch  illustrating  the  process  of  refining  sulphur. 

(See  Chap.  XVII.) 


SULPHUR.  145 


Finally  may  be  mentioned  a  circumstance  which  for  a  long 
time  contributed  to  make  it  peculiarly  interesting  to  the 
alchemist,  if  not  to  ordinary  men:  this  is  the  fact  that  when 
sulphur  is  in  the  pure  form  it  may  be  burned  away  without 
leaving  any  ashes.  In  this  respect  it  differs  from  most  other 
combustible  materials;  and  this  property  created  the  impres- 
sion that  sulphur  is  a  sort  of  principle  of  fire,  and  that  it 
somehow  exists  in  all  combustible  bodies.  Indeed  it  is  only 
for  about  a  hundred  years  that  sulphur  has  been  classified  as  a 
distinct  elementary  form  of  matter.  It  is  not  intended  to 
indicate  here  that  the  strong  interest  of  the  alchemists  in 
sulphur  was  mainly  referable  to  the  circumstances  of  its 
combustibility.  Its  power  of  combination  with  the  metals 
was  well  known  to  them,  and  was  recognized  as  a  subject  of 
practical  importance  and  one  worthy  of  careful  study  and 
thought. 

Natural  Sources  of  Sulphur. 

The  principal  supply  of  sulphur  for  commerce  is  obtained 
from  the  volcanic  districts  of  the  island  of  Sicily.  Here  in 
fact  there  are  more  than  two  hundred  distinct  establish- 
ments for  production  of  the  substance,  and  they  are  capable 
of  yielding  about  two  hundred  million  pounds  of  it  per  year. 

The  fact  that  sulphur  is  easily  and  widely  recognized  in 
the  earth  has  already  been  dwelt  upon.  But  it  occurs  in 
nature  in  a  great  variety  of  forms.  The  first  and  most  strik- 
ing form  is  that  of  free  and  uncombined  sulphur.  In  this 
condition  it  occurs  either  as  masses  or  as  fine  powder.  Some- 
,,  times  these  materials  possess  the  well-known  and  easily 
recognized  yellow  color  of  sulphur;  sometimes,  however,  the 
color  is  white,  or  otherwise  disguised,  by  reason  of  some  pe- 
culiarity of  the  sulphur  itself  or  else  because  of  the  admix- 
ture of  foreign  substances. 

Deposits  of  sulphur  occur  in  the  most  considerable  quanti- 
ties in  the  neighborhood  of  either  active  or  extinct  volcanoes. 
Thus  sulphur  earth  occurs  near  Vesuvius  and  ^Etna,  also  in 
the  ricinity  of  the  volcanoes  of  Iceland,  in  the  crater  of  Po- 
10 


146  CHEMISTRY. 


pocatapetl  in  Mexico,  in  Central  America,  and  in  the  Sand- 
wich Islands. 

In  gathering  sulphur  from  Popocatapetl  a  company  of 
laborers  go  down  into  the  crater.  There  they  gather  the 
sulphur  and  place  it  in  large  buckets,  in  which  it  is  hoisted 
to  the  summit.  They  work  continuously  for  about  a  month, 
eating  and  sleeping  in  the  crater,  until,  completely  exhausted 
by  the  arduous  labor  and  the  sulphurous  fumes  of  the  volcano, 
they  are  hoisted  out  and  rest  while  others  take  their  place. 

In  the  region  of  some  extinct  volcanoes  the  soil  is  impreg- 
nated with  sulphur  to  the  depth  of  twenty  or  thirty  feet,  and 
such  soil  is  therefore  a  convenient  source  of  the  element. 

Purification  of  Natural  Sulphur  Ores. 

In  obtaining  sulphur  from  the  earth  for  commercial  pur- 
poses two  simple  processes  are  resorted  to.  By  the  first 
method,  masses  of  the  sulphur  earth  are  heaped  up  into  a 
pile,  in  connection  with  a  small  amount  of  fuel  and  over  a 
shallow  depression  in  the  earth.  Upon  setting  the  mass  on 
fire  considerable  quantities  of  sulphur  escape  combustion, 
and  so  melt  and  run  down  to  the  ground  below  the  heap. 
When  the  fire  is  extinguished,  the  sulphur  that  collected 
beneath  may  be  secured  in  a  form  now  only  slightly  impure. 

The  second  method  of  purification  of  the  earth  is  still  con- 
ducted in  Sicily  in  the  following  crude  manner,  though  this 
is  quite  an  improvement  upon  that  just  described  :  A 
slightly  inclined  plane  of  masonry  is  built  upon  the  ground. 
Around  the  edges  of  this  plane  a  low  wall  is  erected.  At 
the  lower  side  of  the  plane  the  wall  is  perforated.  Upon  the 
surface  of  the  plane  large  masses  of  sulphur  earth  are  care- 
fully piled  up  so  as  to  form  a  well-built  heap.  When  it 
reaches  the  proper  height  its  outside  is  covered  all  over,  first, 
with  small  fragments  of  the  same  kind  of  earth,  and  then 
with  its  fine  dust.  Sulphur  at  the  lower  portion  of  the  heap 
is  then  set  on  fire  at  several  points.  The  heat  from  the 
sulphur  that  burns  melts  other  portions  of  it,  which  then 
trickle  down  the  spaces  between  the  masses  of  rock.  This 


SULPHUR. 


147 


melted  material,  finding  the  bottom  of  the  pile,  runs  freely 
to  the  lowest  portion  of  the  platform,  then  through  the  per- 
forations and  out  into  wooden  boxes  placed  to  receive  it. 
The  heap  burns  for  two  or  three  weeks,  at  the  end  of  which 
time  the  operation  is  finished.  When  the  mass  is  cool  it  is 
torn  down,  and  a  similar  pile  is  erected  from  fresh  portions 
of  the  sulphur  earth.  The  objectionable  features  of  this  proc- 
ess are  at  least  four.  First,  the  consumption  of  sulphur  as 
fuel  is  a  wasteful  one.  But  in  reply  it  may  be  said  that  no 


FIG.  39.— CaZcarone,  or  heap  of  burning  mineral  from  which  sulphur  is  obtained. 

cheaper  fuel  is  accessible  where  this  manufacture  is  carried 
on.  Again,  the  great  volumes  of  sulphur  dioxide  given  out 
by  the  burning  calcaroni — as  the  heaps  are  called — are  inju- 
rious to  the  health  of  the  workmen.  Further,  these  same 
products  exercise  a  very  destructive  effect  upon  all  vegeta- 
tion in  their  vicinity.  In  fact,  on  this  account  the  Italian 
Government  has  provided  by  law  that  this  work  shall  not  be 
carried  on  at  all  between  July  1  and  December  31.  Finally, 
the  method  is  least  successful  with  the  richest  ores,  for  they 
readily  break  down  into  powder  which  it  is  difficult  to  util- 
ize in  the  calcaroni. 


148  CHEMISTRY. 


A  new  and  greatly  improved  method,  and  one  which  over- 
comes all  the  objections  above  cited,  has  recently  been  intro- 
duced. In  this,  the  ore  is  placed  in  perforated  metal  baskets 
and  then  immersed  in  tanks  containing  hot  solutions  of 
calcic  chloride  in  water.  Under  these  conditions  the  sulphur 
melts  out  from  its  ore  and  falls  to  the  bottom  of  the  tanks 
whence  it  is  drawn  out  by  stop-cocks  in  a  comparatively  pure 
form. 

Sulphur  is  generally  subjected  to  a  still  further  purifica- 
tion. This  is  conducted  somewhat  as  follows:  The  crude 
sulphur,  being  melted  in  a  suitable  retort  and  over  a  coal 
fire,  changes  into  vapor  and  passes  into  an  apartment  con- 
structed of  stone  or  brick,  and  prepared  for  the  purpose.  In 
this  apartment  the  sulphur  at  first  condenses  on  the  walls  as 
minute  yellow  crystals,  or  powder,  called  flowers  of  sulphur. 
When  the  first  charge  of  sulphur  in  the  retort  has  been  com- 
pletely vaporized  a  new  supply  is  allowed  to  run  in,  this 
time  in  the  liquid  form,  from  a  small  heater  placed  above  the 
retort.  The  waste  heat  from  the  furnace  melts  the  sulphur 
in  the  heater,  from  which  it  flows  into  the  retort  (by  means 
of  the  tube  shown  in  Plate  VI).  When  a  sufficient  amount 
of  flowers  of  sulphur  has  collected  in  the  chamber  the  fire  is 
extinguished.  The  purer  product  is  then  removed.  After- 
ward the  whole  operation  is  repeated. 

The  refining  may  be  conducted  so  that  the  temperature  of 
the  condensing  apartment  may  rise  considerably;  in  this  case 
the  vapor  in  it  condenses  to  the  liquid  form.  This  liquid 
may  be  drawn  off  at  the  base  of  the  chamber  into  a  small 
receiver,  from  which  it  is  ladled  into  molds,  which  give  it 
the  form  of  cylinders  known  in  trade  as  roll  brimstone. 

Natural  Compounds  of  Sulphur. 

Sulphur  is  also  found  in  the  earth  in  the  form  of  certain 
chemical  compounds.  Some  of  these  are  very  widely  dis- 
tributed. They  may  be  divided  into  two  classes. 

The  first  class — whose  representatives  are  by  far  the  more 


SULPHUR.  149 


abundant — includes  the  metallic  sulphides,  that  is,  pom- 
pounds  formed  by  the  direct  union  of  sulphur  with  some 
metallic  substance.  As  examples  of  compounds  of  this  class 
we  mention: 

Sulphide  of  iron  (commonly  called  iron  pyrites,  and  having 
the  formula  FeS2). 

Sulphide  of  lead  (commonly  called  galena,  and  having  the 
formula  PbS). 

Sulphide  of  zinc  (commonly  called  blende,  and  having  the 
formula  ZnS). 

Sulphide  of  mercury  (commonly  called  cinnabar,  and  hav- 
ing the  formula  HgS). 

Many  other  examples  of  similar  import  might  be  given, 
for  it  is  a  well-known  fact  that  most  of  the  heavy  metals 
occur  in  the  earth  in  combination  with  sulphur. 

The  other  class  of  compounds  also  containing  sulphur 
combined  with  the  metals  has  usually  oxygen  in  addition. 
Two  examples  of  this  class  may  be  given  here  ;  calcic  sul- 
phate (commonly  called  anhydrite,  and  having  the  formula 
CaSO4);  also  baric  sulphate  (commonly  called  heavy  spar, 
and  having  the  formula  BaSOJ. 

Sulphur  is  very  widely  distributed  in  animal  and  vege- 
table matters.  In  these  it  exists,  not  as  an  uncombined  ele- 
ment, but  in  union  with  others.  Indeed  such  compounds 
have  many  other  elements  besides  the  sulphur,  and  they  are 
characterized  by  decided  complexity  of  structure.  But  sul- 
phur is  oftener  a  component  of  animal  matters  than  of  vege- 
table. The  presence  of  sulphur  in  an  egg  is  proved  by  an 
experiment  of  e very-day  occurrence — that  is  to  say,  the 
silver  spoon  with  which  the  egg  is  eaten  becomes  blackened. 
This  blackening  is  due  to  the  production  of  a  new  compound 
formed  by  a  true  union  of  sulphur  from  the  egg  with  a  part 
of  the  metal  of  the  spoon.  In  fact  the  black  material  is 
sulphide  of  silver,  and  it  may  be  represented  by  the  formula 
Ag2S.  A  French  chemist  has  estimated  that  in  the  body  of 
a  human  being  of  ordinary  size  there  exists,  in  the  aggre- 
gate, not  far  from  one  quarter  of  a  pound  of  sulphur.  To 


150  CHEMISTRY. 


this  he  adds  the  curious  estimate  that  the  entire  human 
population  of  France  may  be  represented  as  containing  not 
far  from  nine  millions  of  pounds  of  sulphur. 

Chemical  Properties  of  Sulphur. 

The  chemical  properties  of  sulphur  may  be  said  to  be  its 
most  important  and  interesting  ones.  That  it  has  a  wide 
range  of  chemical  aptitudes  is  shown  by  the  fact  that  it 
combines  in  simple  forms  of  union  with  a  majority  of  the 
elements  known.  Thus  it  has  strong  affinities  for  most  of 
the  metals.  On  the  other  hand  it  combines  with  various 
degrees  of  attractive  force  with  nearly  all  the  non-metals  as 
well.  Evidently,  then,  sulphur  forms  a  very  large  number 
of  chemical  compounds.  While  the  limits  of  this  work  are 
such  as  to  make  it  impossible  to  describe  many  of  them, 
there  are  three  that  may  with  propriety  be  briefly  discussed 
in  this  place,  and  these  are: 

Sulphuretted  hydrogen     (H2S), 
Sulphur  dioxide  (S02), 

Sulphur  trioxide  (S03). 

Sulphuretted  Hydrogen. 

This  substance  is  a  colorless  gas.  It  has  an  extremely 
offensive  odor;  in  fact  it  is  a  prominent  component  of  that 
numerous  group  of  gaseous  products  of  decomposition  of 
animal  matters  that  produce  the  disagreeable  smell  attend- 
ant upon  the  decay  of  the  latter. 

Again,  it  is  found  in  the  waters  of  certain  natural  sulphur 
springs,  and  it  is  a  remedial  agent  of  considerable  value 
when  properly  applied  externally  or  when  taken  into  the 
stomach.  When  received  into  the  lungs,  however,  it  is  de- 
cidedly poisonous. 

A  considerable  number  of  simple  experiments  may  be 
tried  with  it. 

In  these  the  gas  used  is  generated  by  adding  diluted  sul- 
phuric acid  to  artificial  ferrous  sulphide.  The  ferrous  sul- 


SULPHUR.  151 


phide  is  usually  manufactured  by  heating  a  mixture  of  roll 
brimstone  and  iron  filings  in  a  sand  crucible.  In  producing 
the  gas  the  chemical  change  is  represented  by  the  follow- 
ing equation: 


FeS          -j- 

H2S04 

H2S 

-f         FeSO4 

One  molecule  of 

One  molecule  of 

One  molecule  of 

One  molecule  of 

Ferrous  sulphide, 

Sulphuric  acid, 

Sulphuretted 
hydrogen. 

Ferrous  sulphate, 

88 

98 

34 

152 

parts  by  weight. 

parts  by  weight. 

parts  by  weight. 

parts  by  weight. 

186  186 

For  the  purpose  of  the  experiments  here  mentioned  a 
flask  or  bottle  may  be  used  to  prepare  the  gas  and  convey 
it  into  another  bottle  containing  water.  In  the  water  the 
sulphuretted  hydrogen  gas  dissolves  in  such  quantity  that 
the  solution  so  afforded  may  be  conveniently  employed  for 
showing  the  properties  of  the  gas  itself. 

The  following  interesting  experiments  may  be  performed 
by  use  of  this  solution: 

1.  Dissolve  in  water  a  small  quantity  of  plumbic  acetate, 
also  called  sugar  of  lead.     Filter  this  solution  if  convenient. 
To  the  clear  liquid  add  some  sulphuretted  hydrogen  water. 
A  black  precipitate  of  plumbic  sulphide  (PbS)  should  imme- 
dately  appear. 

2.  Dissolve   in    hydrochloric   acid  a   fragment   of   white 
arsenic  not  bigger  than  a  pin's  head.    To  the  solution  freely 
add  sulphuretted  hydrogen  water.    A  beautiful  lemon-yellow 
precipitate,  consisting  of  arsenious  sulphide  (As2S3),  should 
result. 

3.  Dissolve  in  hydrochloric  acid  a  minute  quantity  of  tar- 
tar-emetic.    To  the  solution  freely  add  sulphuretted  hydro- 
gen water.     A  beautiful  orange-red  and  flaky  precipitate  of 
antimonious  sulphide  (Sb2S3)  should  appear. 

4.  Dissolve  in  water  a  minute  fragment  of  cupric  sulphate, 
commonly  called  sulphate  of  copper  or  blue  vitriol.     To  the 
solution    add    some   of   the   sulphuretted   hydrogen   water. 


152  CHEMISTRY. 


This  should  instantly  give  rise  to  a  black  precipitate  of 
cupric  sulphide  (CuS). 

5.  Dissolve  in  water  a  small  quantity  of  zinc  sulphate.  To 
the  solution  freely  add  sulphuretted  hydrogen  water.  There 
should  appear  in  this  case  a  white  precipitate  consisting  of 
zinc  sulphide  (ZnS). 

These  few  experiments  show  that  sulphuretted  hydrogen 
is  a  convenient  substance  for  bringing  sulphur  into  union 
with  the  metals,  and,  moreover,  they  sustain  the  statements 
already  presented,  that  many  metals  show  strong  affinity  for 
sulphur  and  marked  tendencies  to  combine  with  it.  For 
these  reasons  sulphuretted  hydrogen  is  much  used  in  chem- 
ical laboratories  for  distinguishing  one  metal  from  another.* 

Sulphur  Dioxide. 

When  sulphur  burns  in  oxygen  gas  or  in  atmospheric  air 
it  gives  rise  to  a  new  gas  of  choking  and  offensive  odor. 
This  is  the  same  substance  as  that  produced  in  the  first 
stages  of  the  burning  of  a  sulphur  match.  It  is  a  substance 
of  considerable  importance  in  the  arts,  first,  because  it  is 
always  produced  in  one  stage  of  the  process  used  in  the  man- 
ufacture of  sulphuric  acid.  Now  sulphuric  acid  (commonly 
called  oil  of  vitriol)  is  a  commercial  product  of  enormous 
consumption.  (See  page  156.)  Again,  sulphur  dioxide  is 
used,  as  such,  to  a  considerable  extent  in  the  arts,  the  prin- 
cipal uses  being  in  the  bleaching  of  straw  and  woolen  goods. 
Chlorine  as  a  bleaching  agent  has  already  been  discussed, 
but  it  is  used  mainly  for  the  bleaching  of  cotton  and  linen 
goods;  it  has  an  unfavorable  and  injurious  action  upon  straw 
and  woolen  goods. 

The  way  in  which  these  latter  are  bleached  by  the  use  of 
sulphur  may  be  illustrated  by  a  very  simple  experiment. 
Place  a  few  fragments  of  roll  brimstone  in  a  small  crucible. 
Heat  the  crucible  carefully  until  the  sulphur  takes  fire. 
Then  cover  the  burning  sulphur  with  a  glass  lamp-chimney, 

*  See  Appleton's  Qualitative  Analysis,  published  by  Cowperthwait  &  Co.,  Philadel- 
phia, p.  14. 


SULPHUR.  153 


or  any  other  suitable  contrivance.  In  the  top  of  the  chim- 
ney hang  a  moistened  carnation  pink  or  other  red  flower. 
A  few  minutes'  exposure  to  the  gas  results  in  a  partial 
bleaching  of  the  flower. 

On  a  commercial  scale  the  sulphur  bleaching  process  is 
conducted  in  practically  the  same  manner.  For  bleaching 
woolen  goods  there  is  provided  a  small  wooden  house  having 
a  brick  floor  with  a  small  pit  in  the  center.  The  goods  are 
hung  up  in  this  house.  The  pit  is  filled  with  sulphur  which, 
when  all  is  ready,  is  set  on  fire  by  throwing  a  piece  of  red-hot 
iron  upon  it.  Now  the  doors  and  windows  of  the  house  are 
closed.  Of  course  the  sulphur  burns  into  sulphur  dioxide. 
The  operation  is  allowed  to  proceed  without  any  further 
attention  during  one  night.  The  gas  distributes  itself 
throughout  the  goods  and  bleaches  them.  The  next  morn- 
ing the  doors  and  windows  are  opened,  and,  when  the  fresh 
air  has  driven  the  sulphur  dioxide  from  the  chamber,  the 
goods  are  found  to  be  bleached.  Every  one  knows,  how- 
ever, that  this  bleaching  has  not  the  permanence  that  chlorine 
bleaching  has.  Thus  white  flannels  very  soon  return  to  their 
original  yellowish  shade. 

Sulphur  dioxide  is  placed  by  the  chemist  in  the  class  of 
acid  anhydrides.  This  term  is  intended  to  carry  the  mean- 
ing that  substances  belonging  to  this  class  combine  with 
water  to  form  acids.  In  accordance  with  this  form  of  ex- 
pression, sulphur  dioxide  is  also  called  sulphurous  anhydride. 
Plainly  this  means  that  sulphur  dioxide  with  water  will  form 
an  acid.  Such  seems  to  be  indeed  the  case,  for  water  has 
the  power  of  dissolving  large  quantities  of  sulphur  dioxide, 
and  when  it  does  so  the  water  acquires  the  characteristics  of 
an  acid.  In  fact  it  is  then  called  sulphurous  acid. 

SO2  +  H2O  =  H2SO3 

One  molecule  of  One  molecule  of  One  molecule  of 

Sulphur  dioxide,  Water,  Sulphurous  acid, 

64  18  82 

parts  by  weight.  parts  by  weight.  part*  by  weight. 

82 


154  CHEMISTRY. 


One  special  characteristic  which  justifies  the  name  sul- 
phurous acid  is  the  fact  that  the  solution  so  produced  has 
the  power  of  producing  a  series  of  salts  as  the  other  acids 
do.  In  this  case  the  salts  have  the  general  name  sulphites. 


READING  REFERENCES. 
Sulphur  from  Popocatapetl.     Science,  vi.    p.  390. 
Sulphur  Industry  in  Sicily. 

Barbaglia.  A. — Chem.  News,     xxxiv.  245  ;  xxxv,  3,  28. 
Vincent,  C. — Am.  Chem.  Journal,     vi,  63. 
Sulphur,  Extraction  of. 

Sestini,  F. — Jour.  Chem.  Soc.  of  London,     xxviii,  335. 


SULPHUR   TRIOXIDE.  155 


XVIII. 

SULPHUR     TRIOXIDE. 

lULPHUR  trioxide  does  not  exist  by  itself  in 
nature.  Moreover,  it  is  but  little  known  even  as 
an  artificial  product.  It  is  not  an  article  of  ordi- 
nary sale,  though  it  is  occasionally  made  by  the 
chemist.  Yet  it  is  a  constituent  part  of  one  of  the  most  im- 
portant compounds  known  to  modern  industry.  That  com- 
pound is  sulphuric  acid. 

Sulphur  trioxide  is  a  white  solid,  but  it  cannot  easily  be 
kept  so.  This  is  because  it  has  very  strong  affinity  for  moist- 
ure. In  fact  it  readily  absorbs  that  water  vapor  which  is 
distributed  through  the  atmosphere  even  in  dry  weather, 
and  when  the  ordinary  observer  would  suppose  that  the  air 
contained  no  moisture  at  all.  When  it  absorbs  moisture  it 
chemically  combines  with  it,  forming  sulphuric  acid. 

The  chemical  change  is  represented  by  the  following 
equation  : 

H2S04 

One  molecule  of 

Sulphuric  acid, 
98 

parts  by  weight. 

98 

On  account  of  this  reaction  sulphur  trioxide  is  often  spoken 
of  as  sulphuric  anhydride,  the  term  anhydride  (or  acid  anhy- 
dride, more  properly)  being  intended  to  suggest  that  the  sub- 
stance so  named  is  derived  from  an  acid  by  the  removal  of 
water  from  the  latter.  Thus  sulphuric  acid  minus  water 
produces  sulphuric  anhydride.  And  this  harmonizes  with 
what  has  before  been  declared;  namely,  that  sulphuric  anhy- 
dride —  or  sulphur  trioxide  —  plus  water  produces  sulphuric 
acid. 


SOa                     + 

H20 

One  molecule  of 

One  molecule  of 

Sulphur  trioxide, 

Water, 

80 

18 

parts  by  weight. 

parts  by  weight. 

98 

156  CHEMISTRY. 


Sulphuric  Acid. 

This  substance  is  known  to  commerce  chiefly  under  the 
name  of  oil  of  vitriol.  It  is  an  oily  liquid  nearly  twice  as 
heavy  as  water.  It  has  very  powerful  chemical  action  upon 
most  substances  with  which  it  comes  in  contact.  Moreover, 
its  market  price  is  very  low — that  is,  between  one  and  two 
cents  a  pound  at  wholesale.  To  these  two  facts  last  men- 
tioned— that  is,  the  marked  chemical  power  and  the  low 
price — is  referable  the  enormous  demand  for  the  substance. 
To  be  sure,  increase  of  demand  and  fall  in  price  have  a 
reciprocal  action.  Even  a  slight  cheapening  of  a  substance 
widens  considerably  the  range  of  its  possible  uses,  and 
increases  the  amount  consumed.  Again,  increase  of  demand 
and  consumption  lead  manufacturers  to  increase  their  pro- 
duction, a  circumstance  which  is  generally  followed  by  lower 
price.  The  manufacture  of  sulphuric  acid  exemplifies  these 
well-known  principles  of  political  economy.  The  manufact- 
ure of  this  substance  has  risen  within  the  last  hundred  years 
from  almost  nothing  to  a  present  annual  production  of  about 
nine  hundred  thousand  tons  in  Great  Britain  alone.  The 
price  meanwhile  has  fallen  to  about  one  thirtieth  of  what  it 
was  in  the  middle  of  the  last  century.  At  the  present  time 
the  price  of  oil  of  vitriol  seems  to  be  steadily  decreasing, 
while  the  amount  produced  is  steadily  increasing  in  England, 
France,  Germany  and  the  United  States — indeed  in  all 
countries  pervaded  by  active  industrial  enterprise.  It  will 
be  generally  admitted,  as  M.  Dumas  has  said,  that  the 
amount  of  sulphuric  acid  consumed  affords  a  very  precise 
measure  of  the  advancement  in  industrial  arts  of  a  given 
country  or  of  a  historical  epocli. 

Uses  of  Oil  of  Vitriol. 

It  would  be  difficult  to  enumerate  the  many  industries  that 
demand  the  use  of  sulphuric  acid.  It  must  likewise  be 
admitted  that  there  are  but  few  manufacturing  operations 
which  do  not  directly  or  indirectly  involve  its  employment. 


SULPHUR   TRIOXIDE.  157 

The  industries  that  stand  in  the  front  rank  as  direct  con- 
sumers of  this  acid  are  those  that  involve  the  following 
processes;  namely,  the  bleaching  of  cotton  goods ;  the 
removal  of  scale  from  iron  in  its  various  forms,  such  as  cast- 
ings, wire,  etc.;  the  changing  of  corn  starch  into  the  variety 
of  sugar  commonly  called  glucose;  the  refining  of  bullion  of 
gold  and  silver;  the  refining  of  petroleum  oil;  last,  but  not 
least,  the  manufacture  of  chemical  fertilizers  for  agricultural 
use.  Less  directly,  but  still  in  enormous  quantities,  it  is  used 
in  the  manufacture  of  soda-ash  and  bleaching  powder,  already 
referred  to  as  having  reached  an  incredible  consumption;  in 
the  manufacture  of  alum;  in  the  manufacture  of  both  of  the 
great  acids  of  commerce,  hydrochloric  acid  and  nitric  acid, 
which  must  be  said  to  come  next  to  sulphuric  acid  in  useful- 
ness; and  finally,  in  almost  all  the  distinctly  chemical  indus- 
tries. 

Manufacture  of  Sulphuric  Acid. 

Notwithstanding  the  extremely  low  price  of  oil  of  vitriol 
and  the  immense  quantity  of  it  manufactured  its  production 
implies  a  series  of  processes  far  more  complicated  than  those 
involved  in  the  preparation  of  any  other  well-known  acid. 
Moreover,  although  the  various  intricate  details  of  its  prep- 
aration are  matters  of  thorough  experimental  knowledge  to 
the  producer,  there  are  several  steps  which  are  not  yet 
clearly  comprehended  even  by  the  most  eminent  chemists  of 
the  age. 

The  process  of  manufacture,  as  at  present  conducted,  is 
properly  described  as  a  continuous  one.  By  this  it  is  meant 
that  the  raw  materials  are  steadily  introduced  at  one  end  of 
the  apparatus  used,  and  the  finished  product  is  steadily  drawn 
out  at  the  other,  the'process  meanwhile  going  on  without  inter- 
ruption night  and  day  for  years.  In  order  to  a  better  com- 
prehension of  the  process  it  is  here  described  in  four  stages. 

In  the  first  stage,  sulphur  is  burned  in  a  current  of  air.  The 
material  employ e*d  is  either  partly  refined  Sicily  sulphur,  or, 
what  is  largely  used  at  the  present  day,  some  mineral  com- 


158 


CHEMISTRY. 


pound  of  sulphur,  like  the  iron  and  copper  pyrites.  In  either 
case  sulphur  dioxide  (SO.,)  is  formed.  This  is  the  well-known 
choking  gas  given  out  by  a  burning  sulphur  match.  As  pro- 
duced on  a  large  scale  the  gas  passes  into  a  series  of  enormous 
leaden  chambers.  These  are  in  fact  rectangular  rooms,  often 
as  large  as  one  hundred  and  fifty  feet  long,  twenty  feet  wide 
and  fifteen  feet  high.  Generally  at  least  three  chambers  are 
in  a  series,  connected  by  leaden  pipes.  Sulphur  dioxide  gas 
flows  in  a  steady  stream  into  the  series  of  chambers  and 


FIG.  40.— Section  of  building  fitted  for  manufacture  of  sulphuric  acid :  f.  furnacp 
where  sulphur  is  burned  and  oxides  of  nitrogen  are  liberated ;  /f,  boiler  from  which 
steam  is  supplied  to  the  leaden  chamber,  A. 

toward  the  high  chimney  of  the  works,  whose  draft  produces 
the  advance  of  gases  through  the  whole  apparatus. 

The  second  stage  is  the  most  complicated  one.  It  is  the 
oxidizing  of  the  sulphur  dioxide  (SO2)  into  sulphur  trioxide 
(SO3).  This  is  indeed  accomplished  by  means  of  the  oxygen 
of  the  air.  But  this  oxygen  is  not  capable  of  directly  chang- 
ing SO2  into  SO3.  Certain  gaseous  oxides  of  nitrogen  are 
forced  into  the  chamber  at  this  stage  ;  and  these  have  the 
remarkable  power  on  the  one  hand  of  taking  oxygen  to 
themselves  from  the  air,  and  on  the  other  of  imparting  this 
oxygen  to  the  compound  SO2  in  such  a  way  as  to  change  it 
into  the  compound  SO3.  Of  course  the  air  is  impoverished 


S03                   + 

H20 

One  molecule  of 

One  molecule  of 

Sulphur  trioxide, 

Water, 

80 

18 

parts  by  weight. 

parts  by  weight. 

v 

j 

SULPHUR   TRIOXIDE.  159 

by  the  operation,  a  fact  which  necessitates  a  fresh  supply  of 
it  through  the  entire  series  of  chambers. 

The  third  stage  is  one  whose  principle  has  already  been 
explained.  At  various  parts  of  the  chamber  jets  of  steam 
are  blown  in.  While  these  aid  mechanically  in  the  progress 
of  the  gases  through  the  entire  series  their  main  purpose  is 
to  furnish  water  which  shall  combine  with  sulphuric  anhy- 
dride to  produce  sulphuric  acid. 

Although  the  equation  representing  this  chemical  change 
has  been  given  before  it  may  not  be  improper  to  repeat  it  here: 

H2S04 

One  molecule  of 

Sulphuric  acid, 

98 

parts  by  weight. 

98  98 

The  effect  of  the  steam  is  to  give  rise  to  a  steady  rain  of 
sulphuric  acid  in  the  chambers.  Of  course  this  liquid  collects 
at  the  bottom.  Thence  it  is  drawn  off  to  the  evaporators  for 
treatment  in  a  fourth  stage. 

It  is  plain  that  up  to  this  point  the  series  of  chemical  reac- 
tions takes  place  in  what  we  may  characterize  as  a  vast  but 
irregular  tube,  open  at  both  ends.  This  tube  is  enlarged 
here  and  there  into  great  pockets  which  constitute  the  cham- 
bers. It  is  bent  into  a  form  appropriate  to  the  conditions  of 
the  business.  It  is  entered  here  and  there  by  pipes  for  in- 
troducing the  agents  whose  proper  interaction  gives  rise  to 
the  product  sought.  It  is  also  tapped  for  the  purpose  of 
drawing  off  the  acid  generated.  This  open  tube  has  its  final 
exit  into  the  atmosphere  through  the  tall  chimney  with  which 
it  is  connected.  It  has  its  first  connection  with  the  atmos- 
phere at  the  open  throat,  which  swallows  at  once  the  vast 
volumes  of  sulphurous  gas  from  the  sulphur  burned,  and  at 
the  same  time  levies  upon  the  air  to  contribute  its  oxygen 
to  produce  the  substance  which  is  the  final  purpose  of  the 
whole  industry. 

The  process  thus  far  described  cannot  be  made  to  produce. 


160 


CHEMISTRY. 


acid  of  the  strength  demanded  by  commerce.  In  the  fourth 
stage,  then,  the  acid  from  the  chambers  is  boiled,  with  a  view 
of  expelling  some  of  the  water  in  it,  and  thus  of  producing 
a  more  concentrated  product.  This  evaporation  is  itself  no 
inconsiderable  portion  of  the  business.  It  is  conducted  first 
in  shallow  tanks  of  lead,  and  finally  in  costly  stills  of  platinum. 
When  at  length  the  acid  in  the  platinum  stills  has  attained 
the  proper  degree  of  concentration  it  is  drawn  out  by  means 
of  a  siphon  tube,  and  through  a  cooling  tank  of  cold  water 
into  the  glass  flasks  called  carboys,  in  which  it  makes  its  ap- 
pearance in  commerce. 


FIG.  41.— Section  of  apparatus  used  for  concentrating  sulphuric  acid.  A,  A,  leaden 
pan.s  in  which  the  first  evaporation  is  conducted;  B,  platinum  retort  in  which  the 
concentrating  is  finished. 

Of  course  the  account  thus  given  is  but  a  general  sketch  of 
this  great  industry.  Associated  with  the  apparatus  and  the 
processes  here  briefly  described  there  are  employed  in  actual 
working  a  multitude  of  other  devices  and  operations.  Indeed, 
it  might  be  anticipated  that  the  successful  conduct  of  a  bus- 
iness of  such  magnitude  and  complexity  would  draw  upon 
the  inventive  resources  of  some  of  the  best  minds  that  have 
been  brought  to  bear  upon  chemical  industries. 


READING  REFERENCES. 
Sulphuric  Acid. 

Affleck,  J.— Chem.  News,     xxxvii,  167,  192,  207. 

Hasenclever,  R.— Chem.  News,  xxxv.  48,  67.  88, 118, 183,  189,  214,  227. 


BORON,  161 


XIX. 


BORON. 

|HE  white  substance  called  borax  has  long  been 
known  to  exist  as  a  solid  deposit  in  the  earth  of 
many  parts  of  the  ancient  East.  But  its  uses  have 
increased  a  thousandfold  as  the  result  of  the 
modern  discovery  of  new  and  far  more  abundant  sources  of 
it.  Thus  in  the  manufacture  of  porcelain  and  in  other  of 
the  industrial  arts,  and  as  a  remedial  agency  in  medicine, 
borax  has  now  come  to  be  an  important  and  truly  useful  sub- 
stance to  mankind. 

The  knowledge  of  its  composition  is  referable  to  a  very 
recent  date  ;  it  is  only  in  the  present  century  that  its  char- 
acter as  a  true  chemical  salt  was  fully  made  out.  Borax  is 
now  recognized  as  sodic  borate,  which  usually  exists  in  a 
form  holding  ten  molecules  of  water  of  crystallization  ;  ac- 
cordingly the  chemical  formula  is  Na2B4O7  10  H2O.  From 
this  it  appears  that,  in  addition  to  the  well-known  substances 
sodium  and  oxygen,  borax  contains  a  special  and  peculiar 
element  called  boron  —  a  name  evidently  derived  from  borax. 
Again,  being  a  salt,  the  substance  must  be  viewed  as  contain- 
ing an  acid  —  or,  more  properly  speaking,  the  representative 
of  an  acid.  That  this  is  indeed  the  fact  may  be  readily  proved. 
If  borax  is  dissolved  in  water  in  such  a  way  as  to  form  a  con- 
centrated solution,  then,  upon  addition  of  hydrochloric  acid, 
a  solid  substance  separates  in  pearly  flakes  ;  this  upon  subse- 
quent examination  is  found  to  be  an  acid.  This  solid  acid 
has  received  the  name  boric  acid,  and  it  may  be  represented 
by  the  formula  H3BO3. 

Sources  of  Borax  in  Nature. 

For  a  long  time  the  only  known  source  of  borax  was  the 
natural  crusts  of   this   substance  found  principally  in   the 
11 


164  CHEMISTRY. 


ground  in  certain  parts  of  Asia.  At  the  present  day,  how- 
ever, borax  is  obtained  from  Borax  Lake,  in  California,  in 
very  large  quantities.  In  fact  the  commercial  needs  of  the 
United  States  for  this  substance  are  readily  supplied  from 
borax  found  within  its  own  borders.  The  most  interesting 
and  important  step  in  connection  with  the  preparation  of  borax 
dates  back  to  about  the  year  1776,  when  the  fact  was  made 
public  that  certain  lagoons  in  Tuscany  contained  boric  acid 
in  their  water.  It  was  not  until  about  the  year  1828,  how- 
ever, that  the  manufacture  of  boric  acid  from  this  source 
was  successful  upon  a  large  scale.  In  some  of  the  Tuscan 
valleys  there  are  volcanic  crevices  in  the  earth,  called  suffioni. 
From  them  steam  escapes  charged  with  certain  compounds  of 
boron.  When  this  steam  is  brought  in  contact  with  water 
boric  acid  is  liberated  in  the  water.  The  method  of  secur- 
ing the  acid  is  as  follows  :  a  ring  of  masonry  is  built  in  a 
suitable  place  and  so  as  to  include  several  suffioni.  Some- 
times new  suffioni  are  artificially  bored  within  this  ring. 
Into  the  basin  so  produced  water  from  some  convenient  spring 
is  conducted.  The  steam  from  the  suffioni  passing  into  the 
water  produces  boric  acid  there.  When  the  water  is  suffi- 
ciently charged  it  is  made  to  flow  as  a  gentle  cascade  over 
a  long  series  of  shallow  pans.  The  liquid  readily  evaporates 
from  these  pans,  for  under  them  also  steam  from  suffioni  is 
turned.  It  is  indeed  this  last  mentioned  step  in  the  manu- 
facture that  became  the  turning  point  which  has  led  to  its 
successful  prosecution.  The  great  cost  of  fuel  for  artificially 
evaporating  the  acid  liquors  rendered  unprofitable  the  earlier 
attempts  to  utilize  this  source  of  boric  acid.  A  French  gentle- 
man, M.  Larderel,  suggested  the  use  of  steam  from  suffioni 
for  the  evaporation  of  the  liquids  produced,  and  the  process 
was  so  successful  that  he  quickly  derived  a  colossal  fortune 
from  its  employment.  At  the  same  time  he  enriched  the 
territory  that  was  previously  not  only  desert  and  unproduc- 
tive, but  also  was  looked  upon  by  the  inhabitants  with  super- 
stitious dread,  and  as  little  better  than  the  gate  of  the  infernal 
regions.  As  a  result  of  these  inventions  a  barren  and  mi- 


frequented  territory  has  been  changed  to  a  seat  of  thriving 
and  beneficial  industry.  Finally,  it  is  interesting  to  note 
that  for  his  services  in  developing  the  boric  acid  industry 
M.  Larderel  was  created  Count  of  Monte-Cerboli  by  the 
Grand  Duke  of  Tuscany. 


READING  REFERENCES. 

Boric  Acid,  Manufacture  of,  etc. 

Payen.— Annales  de  Chimie  et  de  Physique.  3  Sur.  i,  247  ;  ii,  322. 
Dieulafait,  L.— toe.  sit.  5  Ser.  xii,  318;  xxv,  145. 

Borax  Lagoons  of  Tuscany. 

Harper's  Magazine,  i,  397. 

Borax  of  California,  history  of. 

Robottom,  Arthur.— Chem.  News,  liv,  244. 


106 


XX. 

NITROGEN. 

lITROGEN  is  an  important  constituent  of  our  atmos- 
pheric air,  of  which  it  makes  up  about  eighty  per 
cent. ;  the  other  twenty  per  cent,  being  oxygen. 
In  the  air  the  nitrogen  is  found  in  the  free  or  un- 
combined  state,  and  we  may  reasonably  suppose  that  it  exists 
here  to  fulfill  some  important  offices.  Unquestionably  one 
of  these  is  that  of  diluting  the  oxygen,  the  energetic  constit- 
uent of  air,  and  lessening  its  activities — for  nitrogen  itself 
is  extremely  inert.  From  the  part  it  performs  in  the  atmos- 
phere nitrogen  derives  a  considerable  portion  of  the  interest 
with  which  it  is  invested. 

Discovery  of  Nitrogen. 

Perhaps  the  first  clearly  defined  recognition  of  nitrogen  as 
a  constituent  of  the  air  is  referable  to  the  genius  of  a  wonder- 
ful man,  who,  in  obscurity  and  with  very  simple  apparatus, 
obtained  an  insight  into  the  constitution  of  substances  which 
has  rarely  been  surpassed.  Reference  is  here  made  to  the 
Swedish,  or  rather  Prussian,  chemist  Scheele,  some  of  whose 
discoveries  have  been  briefly  adverted  to  in  earlier  chapters. 
It  has  already  been  stated  that  the  distinct  notion  of  a  gas 
dates  but  little  more  than  a  hundred  years  back  ;  and  this 
statement  is  intended  to  call  to  mind  that  brilliant  period  in 
the  history  of  chemistry  when,  among  others,  Black  in  Scot- 
land, Cavendish  and  Priestley  in  England,  Lavoisier  and  his 
worthy  associates  in  France,  and,  finally,  the  sagacious  Scheele 
in  Sweden,  were  engaged  in  a  generous  rivalry  in  chemical 
studies,  which  made  the  close  of  the  eighteenth  century  a 
period  in  the  history  of  chemistry  that  will  not  be  forgotten 
so  long  as  the  science  itself  shall  endure.  At  this  time  un- 


NITROGEN.  167 


stinted  effort  was  devoted,  with  ingenious  but  imperfect 
appliances,  to  the  study  of  gases.  Of  course  the  atmospheric 
air,  as  the  gas  most  vast  in  quantity,  most  accessible  for  ex- 
periment, most  important  in  its  relation  to  the  economy  of 
living  beings,  received  its  full  share  of  attention.  It  was  at 
this  period  that  Dr.  Rutherford,  a  professor  in  the  University 
of  Edinburgh,  demonstrated  that  after  living  animals  have 
breathed  in  a  confined  bulk  or  volume  of  air  there  remains 
an  inert  and  peculiar  gas  behind.  And  Priestley  showed 
that  after  the  burning  of  charcoal  in  a  confined  volume  of  air 
there  remains  a  gaseous  material  equal  to  about  four  fifths 
of  the  amount  of  original  air  used.  But  it  was  Scheele  who 
first  clearly  pointed  out  that  the  air  contains  a  second  distinct 
constituent  that  fails  to  support  combustion  and  animal  res- 
piration. And  Lavoisier  first  proved  this  constituent  to  be  an 
elementary  substance,  and  he  gave  to  it  the  name  azote, 
which  it  still  retains  in  the  French  nomenclature  of  chem- 
istry, and  which  is  also  used  (in  composition)  in  many  En- 
glish chemical  terms  to  express  the  nitrogenous  constituent. 
It  is  not  forgotten  that  a  critical  examination  of  the  history 
of  human  knowledge  respecting  the  atmosphere  reveals  the 
fact  that  a  wonderfully  clear,  even  though  incomplete,  ac- 
count of  the  functions  of  the  active  constituent  of  the  air  was 
printed  as  early  as  the  year  1669,  by  an  English  physician 
named  John  Mayow.*  This  affords  another  illustration  of 
the  fact,  recognized  by  all  students  of  history,  that  often,  in 
the  progress  of  knowledge,  before  the  clear  and  full  dawn 
there  seems  to  be  a  twilight;  at  such  a  time,  and  before  the 
darkness  has  been  fully  dispelled,  there  have  been  found  here 
and  there  men  gifted  with  supernatural  mental  vision  who 
have  been  able  to  read  the  laws  of  nature  long  before  acknowl- 
edged philosophers,  even,  had  found  light  sufficient.  And  so 
the  truths  learned  by  Mayow,  though  clearly  stated  by  him, 
failed  of  recognition  until  they  were  rediscovered  a  hundred 
years  later.  (See  p.  113.) 

*KOPP,  HERMANN  :  Qeschichte  der  Chemie.  Dritter  Thell.  s.  193. 


168 


CHEMISTRY. 


Preparation  of  Nitrogen. 

Nitrogen  is  usually  prepared  from  the  air  by  the  with- 
drawal of  oxygen  from  it.  This  withdrawal  is  effected  by 
some  substance  which  has  a  strong  affinity  for  oxygen. 

One  method  frequently  resorted  to  is  to  burn  phosphorus 
in  air.  Phosphorus  is  placed  in  a  little  crucible  of  porcelain 
and  then  floated  upon  a  cork  on  the  surface  of  water  in  a 
pneumatic  trough.  A  bell-glass  of  air  is  now  inverted  over 


FIG.  44— Preparation  of  nitrogen  from  air,  by  absorbing  the  oxygen  by  burning 
phosphorus. 

the  phosphorus,  after  the  latter  has  been  set  on  fire.  The 
phosphorus  burns  at  the  expense  of  the  oxygen  in  the  bell- 
glass.  Thus  the  oxygen  is  little  by  little  withdrawn,  and  as 
a  result  the  nitrogen  is  left.  Another  method  for  preparing 
nitrogen  is  based  upon  the  same  general  principle.  It  is  the 
following  :  pass  a  current  of  dry  air  through  a  tube  contain- 
ing copper  turnings  heated  to  dull  redness  in  a  furnace. 
Under  these  circumstances  the  copper  absorbs  oxygen  from 
the  air,  and  leaves  the  nitrogen,  which  passes  on  to  a  receiver 
prepared  for  it. 


NITROGEN.  1G9 


Properties  of  Nitrogen. 

Nitrogen  prepared  by  these  methods,  or  by  any  others,  pos- 
sesses the  following  characteristics  : 

It  is  a  gas  that  is  colorless,  odorless  and  tasteless.  It  is 
not  necessary  to  make  any  scientific  demonstration  of  these 
facts,  because  with  every  breath  of  air  drawn  into  the  lungs 
of  a  human  being  a  large  quantity  of  nitrogen  is  inhaled, 
and  it  is  easily  perceived  to  be  without  odor  or  taste,  while 
a  glance  of  the  eye  into  the  atmosphere  shows  that,  in  moderate 
quantities,  at  least,  it  is  free  from  color.  Up  to  a  period  dnt- 
ing  but  a  few  years  back  nitrogen  was  spoken  of  as  one  of 
the  permanent  gases  ;  and  this  word  permanent  was  intended 
to  convey  the  idea  that  it  is  not  condensable  to  the  liquid 
form.  It  is  true  that  it  was  surmised  that  for  every  gas  there 
must  be  a  point  of  very  low  temperature  and  very  great 
pressure  at  which  the  gas  would  assume  the  liquid  form. 
Yet  nitrogen,  and  two  or  three  others,  resisted  all  such  at- 
tempts to  liquefy  them  until  toward  the  close  of  the  year  1878. 
Since  that  time  successful  effort  has  been  made  to  bring  to 
a  higher  degree  of  perfection  the  appliances  used  for  sub- 
jecting gases  at  once  to  intense  cold  and  enormous  pressure. 
With  these  it  is  believed  that  small  amounts  of  nitrogen  have 
been  liquefied.  And  it  may  even  be  said  that  there  is  now 
no  permanent  gas  known,  but  that  all  gaseous  substances 
may  in  fact  be  liquefied.* 

As  a  simple  and  uncombined  substance  nitrogen  is  char- 
acterized by  extreme  inactivity.  It  does  not  burn  ;  it  does 
not  support  combustion  ;  it  cannot  be  made  to  enter  into 
chemical  union  with  other  substances,  except  by  specially 
devised  and  circuitous  processes. 

While  on  the  one  hand  inertness  is  the  mnrked  character- 
istic of  the  nitrogen,  on  the  other  hand  this  element  is  a 
constituent  of  a  very  large  number  of  compounds.  Moreover, 
these  compounds  are  themselves  often  characterized  by  a 
high  degree  of  activity.  Of  the  last  two  declarations  the 

*  SCHIJTZENBERGER,  PAUL  :  Traiti  de  Chimie  Generate,  Paris,  1880,  i,  30. 


170  CHEMISTRY. 


first  one  seems  to  be  inconsistent  with  the  properties  of  nitro- 
gen in  its  elemental  form.  The  second  one  seems  inconsist- 
ent, but  less  so  when  it  is  carefully  considered.  Thus  the 
activity  of  the  compounds  of  nitrogen  is  to  a  certain  extent 
referable  to  their  instability.  The  meaning  of  instability, 
as  used  here,  is  that  the  compounds  are  easily  decomposed  ; 
and  this  is  because  the  inert  nitrogen  readily  lets  go  its  hold 
upon  the  other  elements.  Whence  it  appears  that  the  ac- 
tivity of  the  compounds,  is  really  referable  to  the  energetic 
action  of  the  element  or  elements  now  loosed  from  the  nitro- 
gen, rather  than  to  the  nitrogen  itself. 

In  nature  nitrogen  is  found  as  a  constituent  in  some  very 
important  compounds.  Thus  it  seems  to  be  an  essential 
element  of  some  of  the  principal  animal  matters,  such  as  mus- 
cular fibre  and  the  material  of  the  brain.  Again,  it  is  a  con- 
stituent of  ammonia  gas  and  also  of  a  multitude  of  compounds 
derived  from  it.  Now  these  compounds  are  members  of  a 
group  of  substances  which  serve  as  most  valuable  kinds  of 
food  for  living  plants.  So  it  may  be  said  that  both  living 
animals  and  plants  seem  to  be  in  a  peculiar  way  dependent 
upon  nitrogen  or  nitrogenous  matters. 

Compounds  of  Nitrogen  and  Hydrogen. 

Properly  speaking,  only  two  compounds  of  nitrogen  and 
hydrogen  are  known  : 

Diamidogen  (Hydrazine.)  2XH2  (or  N2H4). 

Ammonia  Gas.  NH3. 

A  third  compound  called  ammonium  (NH4),  and  viewed 
as  a  hypothetical  metal,  is  often  referred  to.  Since,  however, 
this  substance  is  at  present  known  only  in  combination  with 
other  elements  it  must  be  considered  as  having  a  theoretical 
rather  than  a  real  existence. 

Hydrazine. 

This  substance  is  a  colorless  gas  which,  when  mixed  with 
much  air,  has  but  little  odor;  when  concentrated,  however, 


NITROGEN.  171 


it  has  a  very  irritating  influence  upon  the  mucous  membranes 
of  the  nose  and  throat.  It  is  of  chief  interest  to  chemists  be- 
cause of  its  history.  From  certain  compounds  containing  ni- 
trogen, hydrogen,  and  other  substances,  it  has  long  been  recog- 
nized that  the  group  of  atoms  represented  by  the  expression 
NH2  has  a  kind  of  integrity  which  suggested  the  possibility  of 
its  separate  existence.  It  was  not  practicable,  however,  to 
produce  it  as  a  separate  compound  until  very  recently.  Theo- 
dor  Curtius  has  within  a  short  time  announced  that  he  has 
prepared  the  substance,  and  he  has  described  his  method. 

Ammonia  Gas. 

Under  favorable  circumstances  nitrogen  and  hydrogen 
combine  to  form  the  stable,  interesting  and  important  com' 
pound  called  ammonia  gas,  and  having  the  formula  NH3. 

While  the  gas  may  be  produced  by  the  direct  union  of  the 
constituents — that  is,  wrhen  a  mixture  of  nitrogen  gas  with 
hydrogen  gas  has  an  electric  discharge  slowly  passed  through 
it — this  is  not  a  common  mode  of  procedure.  Ammonia  gas 
is  oftener  produced  by  a  natural  or  artificial  decomposition 
of  certain  substances  that  contain  nitrogen  and  hydrogen 
among  their  constituents.  As  it  has  already  been  stated  that 
many  animal  matters  contain  nitrogen  and  hydrogen,  it  fol- 
lows that  animal  matters  when  decomposed  afford  ammonia 
gas  ;  and  so  they  do,  in  fact,  whether  the  decomposition  is 
in  the  course  of  their  natural  decay,  or  whether  it  is  con- 
ducted artificially,  as,  for  example,  when  animal  matters  are 
heated  in  closed  vessels  to  the  point  of  decomposition.  In- 
deed ammonia  gas  and  its  important  commercial  compounds 
were  formerly  produced  in  this  last-mentioned  manner. 

Ammonia  gas — or  some  compound  of  it — is  also  formed, 
as  may  be  readily  imagined  from  what  has  already  been  said, 
from  decomposition  of  vegetable  matters  containing  nitrogen. 
It  is  a  fact  that  at  the  present  day  the  principal  supplies  of 
ammonia  gas  and  its  compounds  for  the  uses  of  commerce 
and  the  arts  come  from  such  a  source — that  is,  from  the  arti* 


172  CHEMISTRY. 


ficial  decomposition  of  bituminous  coal.  It  is  true  that  in 
the  ordinary  sense  coal  is  not  vegetable  matter.  But  careful 
examination  of  it  shows  that  it  is  very  directly  derived  from 
the  vegetation  of  ancient  forests.  The  vegetable  matter  has 
been  packed  away  in  the  earth  and  has  been  subjected  to 
water,  heat  and  pressure  under  such  conditions  that  these 
agencies  have  changed  it  to  the  form  in  which  we  find  it. 
Now  the  coal-gas  industry  of  the  present  day  is  so  conducted 
as  to  decompose  coal  and  collect  many  of  the  products  of  its 
decomposition.  One  of  these  products  is  ammonia  gas.  To 
the  decomposition  of  coal,  therefore,  the  business  world  at 
present  looks  for  its  supply  of  ammonia  gas  and  the  many 
compounds  derived  from  it. 

The  name  ammonia  gas  indicates  that  it  ordinarily  exists 
in  the  aeriform  condition.  It  has  a  very  pungent  odor,  well- 
known  as  that  evolved  from  smelling-salts.  It  dissolves  in 
water  with  very  great  facility  and  in  very  large  quantities. 
It  has  a  strong  tendency  to  combine  with  acids.  This  last 
fact  may  be  easily  illustrated  by  simple  experiments  within 
the  reach  of  almost  any  one. 

Experiment  with  Ammonia. 

Provide  two  wine-glasses,  or  two  shallow  vessels  of  any 
sort.  Into  one  of  them  pour  the  liquid  known  as  spirits  of 
hartshorn,  and  called  by  the  chemist  ammonic  hydrate.  Into 
the  other  pour  some  concentrated  hydrochloric  acid.  Abun- 
dant white  clouds  will  quickly  form  above  the  vessels  and 
between  them.  These  clouds  are  composed  of  minute  par- 
ticles of  a  solid,  called  by  the  chemist  ammonic  chloride  and 
expressed  by  the  formula  NH4C1.  The  reason  for  their  for- 
mation is  this  :  from  the  spirits  of  hartshorn  escapes  ammo- 
nia gas  (NH3);  from  the  acid  there  constantly  escapes 
hydrochloric  acid  gas  (HC1 ) ;  the  two  gases  meeting  in  the 
atmosphere  combine  with  energy  and  form  the  smoky  prod- 
uct referred  to. 

The  chemical  change  is  represented  by  the  following 
equation  : 


NITROGEN.  173 


NH3              H 

HC1 

NH4C1 

One  molecule  of 

One  molecule  of 

One  molecule  of 

Ammonia-gas, 

Hydrochloric  acid, 

Ammonic  chloride, 

17 

36£ 

53£ 

parts  by  weight. 

parts  by  weight. 

parts  by  weight. 

The  ammonic  chloride  thus  produced  is  an  article  of  com- 
merce, well-known  under  the  name  sal  ammoniac.  As  has 
been  said,  it  is  a  solid,  and  it  belongs  to  the  class  of  sub- 
stances designated  by  chemists  as  salts.  In  fact,  one  of  the 
most  striking  characteristics  of  ammonia  gas  is  its  power  to 
produce  salts  by  union  with  acids.  Here  is  a  list  of  three 
well-known  salts  of  this  sort : 

With  Hydrochloric  acid,  HC1        it  produces  Ammonic  chloride,  NII4C1. 
"     Nitric  acid,  HN03     it  produces  Ammonic  nitrate,    NH4N03. 

"     Sulphuric  acid,         H2S04    it  produces  Ammonic  sulphate,  (NH  i)2S04. 


Commercial  use  of  Ammonia  Gas. 

One  of  the  chief  uses  of  the  ammonia  afforded  by  the  illu- 
minating gas  industry  is  in  machines  for  producing  ice  arti- 
ficially. 

The  general  principle  of  these  machines  may  be  stated  as 
follows  :  By  powerful  pumps  they  compress  ammonia  gas  to 
the  liquid  form  and  the  heat,  called  latent  heat,  of  the  gas  is 
now  freely  evolved,  and  it  is  carried  away  by  an  abundant 
stream  of  flowing  water.  The  liquid  ammonia  is  next  trans- 
ferred to  the  jacketed  space  surrounding  the  relatively  small 
amount  of  water  which  is  to  be  frozen. 

By  the  working  of  the  ice  machines  this  liquid  ammonia 
vaporizes ;  it  now  begins  to  absorb  heat  in  amount  equiva- 
lent to  the  latent  heat  it  previously  evolved.  The  machine 
is  so  adjusted  that  the  ammonia  shall  absorb  this  heat  from 
the  small  amount  of  water  to  be  frozen.  This  water  being 
deprived  of  heat  is  so  much  reduced  in  temperature  that  it 
reaches  the  freezing  point,  and  thereupon  solidifies. 


174  CHEMISTRY. 


Compounds  of  Nitrogen  and  Oxygen. 

Nitrogen  and  oxygen  ordinarily  manifest  scarcely  any  af- 
finity for  each  other.  There  are  conditions,  however,  under 
which  they  unite  ;  and,  moreover,  they  unite  in  different  pro- 
portions so  as  to  form  at  least  five  different  compounds. 
These  may  be  presented  in  the  form  of  the  following  striking 
series  : 

Nitrogen  protoxide  (called  laughing-gas,)  N20. 

Nitrogen  dioxide,  N202  (or  NO). 

Nitrogen  trioxide  or  nitrous  anhydride,  N203. 

Nitrogen  tetroxide  (brown  fumes,)  N204  (or  N02). 

Nitrogen  pentoxide  or  nitric  anhydride,  N205. 

Of  these  compounds  unquestionably  the  most  important 
is  nitric  anhydride —  and  this  not  on  account  of  itself,  for  it 
is  very  rarely  produced  either  in  the  arts  or  in  the  investi- 
gator's laboratory.  Its  importance  is  referable  to  the  fact 
that,  added  to  water,  it  produces  nitric  acid. 

This  chemical  change  is  represented  by  the  following 
equation  : 

N2O5  +  H2O  2HNO:i 

One  molecule  of  One  molecule  of  Two  molecules  of 

Nitric  anhydride,  Water,  Nitric  acid, 

108  18  126 

parts  by  weight.  parts  by  weight.  parts  by  weight. 


126  126 

Nitric  Acid. 

This  acid  has  been  referred  to  in  another  place  as  one  of 
three  principal  acids  of  commerce.  Certain  of  its  most  strik- 
ing properties  may  be  displayed  in  an  easy  interesting  man- 
ner by  any  one.  For  this  purpose  the  following  experi- 
ments are  suggested  : 

First  experiment. — Nitric  acid  turns  quill  yellow. 

Place  a  few  fragments  of  white  quill  in  a  test-tube.  Add 
a  few  drops  of  nitric  acid  and  then  some  water.  Now  warm 
the  mixture.  The  quill  will  be  found  to  acquire  a  yellow 


NITROGEN.  175 


color.  Fill  the  tube  with  cold  water  in  order  both  to  dilute 
the  acid  and  to  cool  it.  Pour  away  the  liquid  and  wash  the 
quill  in  water.  The  yellow  color  will  be  found  to  be  perma- 
nent. Many  other  animal  matters  are  turned  to  a  permanent 
yellow  color  by  nitric  acid. 

Second  experiment. — Nitric  acid  attacks  copper  with  vio- 
lence. There  is  liberated  by  the  process  a  gas  called  nitrogen 
dioxide  (N2O2),  which  is  colorless  but  which  becomes  brown 
upon  exposure  to  the  atmospheric  air.  The  chemical  change 
gives  rise  to  a  solution  sometimes  green  and  sometimes  blue, 
according  to  circumstances. 

Place  in  a  test-tube  a  small  piece  of  metallic  copper  in  the 
form  of  either  wire  or  foil.  Add  some  nitric  acid  to  the  cop- 
per. Then  warm  it  gently  until  the  copper  disappears.  The 
brown  fumes  will  be  recognized.  The  colored  solution  of 
cupric  nitrate,  Cu  (N03)2  should  also  be  noticed. 

Third  experiment. — Nitric  acid  attacks  zinc  with  great 
violence. 

Try  another  experiment  quite  similar  to  that  just  described, 
only  employ  zinc  in  place  of  copper.  Brown  fumes  are 
evolved,  and  a  colorless  solution  is  produced  containing  zinc 
nitrate,  Zn  (NO3)2. 

Fourth  experiment. — Nitric  acid  attacks  iron  with  violence. 

Try  another  experiment,  quite  similar  to  the  second  and 
third,  only  employ  iron  instead  of  the  other  metals  men- 
tioned. The  fine  iron  wire  used  by  florists  is  suitable  for 
this  purpose.  The  same  brown  fumes  are  evolved.  A  me- 
tallic nitrate  is  also  produced  ;  it  is  called  ferric  nitrate  and 
its  formula  is  Fe2(NO3)6.  The  solution  is  yellow,  or  but 
slightly  colored. 

Fifth  experiment. — Nitric  acid  dissolves  a  nickel  coin. 

An  experiment  similar  to  those  already  detailed  may  be 
tried  upon  a  nickel  coin  ;  but  it  is  not  necessary  to  entirely 
dissolve  the  coin.  After  the  acid  has  acted  for  a  few 
moments  water  may  be  poured  into  the  tube  so  as  to  diluto 
the  acid  and  at  the  same  time  to  cool  it.  Then  the  liquid 
may  be  poured  away  and  the  coin  withdrawn,  In  addition 


176  CHEMISTRY. 


to  the  brown  fumes  evolved,  the  feature  most  noticeable  is 
the  decided  green  color  of  the  solution.  This  is  referable,  to 
a  considerable  degree  at  any  rate,  to  the  nickel  present. 
Nickel  imparts  a  green  color  to  most  of  its  solutions. 

These  experiments  suggest  that  nitric  acid  has  a  marked 
influence  upon  the  metals.  This  is  in  fact  one  of  its  promi- 
nent characteristics ;  and  it  is  largely  used  in  the  arts  for  the 
purpose  of  dissolving  metals. 


READING  REFERENCES. 

Nitrogen,  Chemistry  of 

— Prescott,  A.  B. — Jour.  Araer.  Chem.  Soc.  ix,  128. 

Diaraide  (hydrazine) 

— Curtius,  T.— Chem.  News.  lv,  288 ;  Ainer.  Chem.  Jour,  ix,  300. 


THE  ATMOSPHERE.  177 


THE    ATMOSPHERE. 

|HE  atmosphere  or  the  air  of  our  globe  is  the  vast 
ocean  of  gaseous  matter  at  the  bottom  of  which 
human  beings,  as  well  as  other  land  animals, 
dwell.  While  it  is  so  thin  that  a  vessel  full  of  it 
is  spoken  of  in  ordinary  language  as  being  empty,  it  yet  pos- 
sesses a  reality  which  it  often  displays  in  a  very  serious  man- 
ner. Its  presence  is  made  gently  evident  to  human  beings 
by  the  moderate  resistance  it  offers  to  them  when  they  are  in 
motion ;  but  when  itself  is  in  motion  with  the  force  of  the 
hurricane  or  tornado  no  solid  matter  can  stand  in  its  path. 
Heavy  railroad  trains  and  massive  buildings  are  hurled  from 
their  positions  and  turned  into  miserable  masses  of  wreck- 
age, while  even  strongly  rooted  forests  are  swept  out  of  place 
by  its  vigorous  breath.  The  terribly  destructive  power  of 
air  at  one  moment  and  its  mild  and  subtle  efficiency  at  another 
are  very  suggestive  of  the  wonderful  adjustment  of  the  forces 
residing  in  it.  It  is  by  the  restrained  action  of  these  forces 
that  the  atmospheric  air  is  so  admirably  fitted  to  perform  its 
varied  functions  in  connection  with  animal  life.  At  the  same 
time  it  is  so  unobtrusive  in  its  workings  that  its  very  existence 
is  at  first  scarcely  noted.  When  at  rest  it  peacefully  wraps 
the  earth  about  as  in  a  gossamer  veil,  but  when  in  angry 
agitation  it  scourges  country  and  city  alike  as  with  a  whip  of 
gigantic  cables. 

The  height  to  which  the  atmospheric  air  extends  above 
the  earth  is  not  exactly  known.  But  carefully-devised  ex- 
periments have  shown  that,  going  upward,  its  compactness  or 
density  diminishes  very  rapidly.  Indeed,  calculations  based 
upon  exact  experiment  show  that  at  a  height  of  forty  miles, 
or  thereabouts,  from  the  surface  of  the  earth,  the  air  is  so 
highly  rarefied  that  practically  it  there  comes  to  an  end.  In 
12 


178  CHEMISTRY. 


other  words,  at  this  height  a  given  bulk  of  space  contains  no 
more  air  than  exists  in  the  so-called  vacuum  produced  by  a 
superior  air-pump. 

Weight  of  Air. 

Notwithstanding  the  extreme  tenuity  of  the  gaseous 
medium  in  which  we  live,  it  is  capable  of  buoying  up  on  its 
wings  a  multitude  of  living  beings  of  vast  aggregate  weight. 
It  is  firm  enough  to  support  the  millions  of  birds  that  sail  in 
it,  and  the  myriad  of  millions  of  insects  who  yet  more  freely 
navigate  it  in  search  of  food  and  warmth,  and  in  answer  to 
the  various  needs  of  their  existence. 

One  of  the  most  striking  evidences  of  the  fact  that  air  is 
indeed  a  material  substance  is  very  easily  discovered  by 
showing  that  it  possesses  weight.  Thus,  suppose  a  properly 
constructed  glass  globe  is  almost  entirely  emptied  of  air  by 
the  action  of  an  efficient  air-pump.  Suppose  then  that  the 
globe  is  weighed.  Next  if  it  be  connected  with  a  bell-glass 
containing  ordinary  atmospheric  air  over  a  pneumatic  trough, 
it  may  be  readily  seen  that  the  air  leaves  the  bell-glass  in 
order  to  pass  into  the  globe.  If  this  globe  is  now  weighed 
again  it  is  found  to  manifest  a  decided  increase  of  weight 
This  increase  is  due  to  the  air  it  has  received.  By  such 
means  it  may  be  easily  showrn  that  a  cubic  yard  of  air  weighs 
not  far  from  twro  pounds. 

Composition  of  Air. 

The  principal  constituents  of  air  are  the  two  gases,  oxygen 
and  nitrogen ;  and  of  these  the  oxygen  makes  up  about  one 
fifth  and  the  nitrogen  about  four  fifths  of  the  whole.  In  ad- 

£3 

dition  to  these  principal  substances,  however,  certain  others 
are  always  present,  of  which  may  be  specified  vapor  of  water, 
carbon  dioxide  and  ammonia  gas ;  while  more  minute  quan- 
tities of  a  vast  multitude  of  other  gaseous  substances  find  a 
reservoir  in  the  air.  It  is  an  unquestioned  fact  that  the 
atmosphere  is  likewise  charged  most  of  the  time  with  still 
more  minute  quantities  of  solid  dust  materials  of  various  kinds. 


THE  ATMOSPHERE.  179 

An  example  is  found  in  the  common  salt,  blown  up  into  the 
atmosphere  from  the  ruffled  surface  of  the  oceans.  Now 
the  oceans  are  spread  over  fully  three  fourths  of  the  earth's 
surface,  and  the  winds,  blowing  upon  the  crested  waves,  not 
only  diffuse  the  salt  over  the  oceans  themselves  but  also  carry 
it  far  inland  ;  accordingly  spectrum  analysis  reveals  the  pres- 
ence of  salt  in  almost  all  atmospheric  air. 

Just  as  the  rivers  of  water  flow  to  the  ocean  and  bear 
along  to  it  debris  of  every  kind — pulverized  rock  and  earthy 
materials  and  other  washings  from  the  soil,  leaves  of  forests, 
impure  products  of  civilization  thrown  in  from  houses  and 
manufacturing  establishments — and  all  these  materials  make 
their  relatively  minute  contributions  to  the  impurities  in  the 
great  ocean  itself,  so  it  is  with  the  atmospheric  ocean. 
Thousands  of  millions  of  living  animals  pour  out,  with  every 
breath  from  the  lungs,  materials  exhaled  from  their  bodies. 
And  so  wherever  fuel  is  burned,  or  wherever  manufacturing 
establishments  liberate  gases  or  vapors,  or  even  finely  pul- 
verized solids,  these  are  cast  forth  from  the  mouths  of  reek- 
ing chimneys  ;  and  they  all  flow  into  the  great  aerial  sea. 
So  then  it  is  no  unexpected  circumstance  that  the  air  should 
be  a  reservoir  in  which,  in  minute  quantity,  is  likely  to  exist 
every  gaseous  substance  produced. 

Offices  of  the  Several  Constituents  of  the  Air. 

The  oxygen  of  the  air  is  its  most  active  constituent.  This 
is  the  substance  that  has  already  been  described  as  essential 
for  all  ordinary  combustion  and  all  animal  respiration.  By 
a  great  variety  of  characteristics  it  is  well  fitted  for  these 
important  offices. 

The  chief  duty  of  the  nitrogen  appears  to  be  to  dilute  the 
oxygen  and  moderate  the  excessive  activities  that  would  be 
manifested  if  the  atmosphere  consisted  entirely  of  the  active 
gas.  Since  iron  and  other  metals  burn  in  pure  oxygen,  it  is 
plain  that  in  an  atmosphere  of  oxygen — containing  no  mod- 
erating gas  like  nitrogen — a  fire  once  kindled  in  a  stove 


180  CHEMISTRY. 


would  not  confine  itself  to  its  proper  fuel,  but  would  soon 
spread  to  the  metal  of  the  stove  itself,  and  so  initiate  con- 
flagrations that  could  hardly  be  restrained. 

The  moisture  in  the  air  adds  a  number  of  wonderful  and 
serviceable  characteristics  to  it.  Thus  it  helps  to  retain  the 
heat  received  from  the  sun  and  so  materially  contributes  to 
the  sustenance  of  animal  and  vegetable  life.  The  heat  of 
the  sun  penetrates  our  atmospheric  coverlet  with  great  readi- 
ness and  this  heat  is  received  by  the  surface  of  the  earth  and 
thence  is  imparted  to  the  layer  of  air  immediately  upon  it. 
Now  the  moisture  contained  in  the  atmosphere — and  in  prin- 
cipal quantity  in  the  portions  of  air  closest  to  the  earth — is 
one  of  the  chief  agencies  that  prevent  the  immediate  escape 
of  that  heat  that  the  solid  earth  has  secured  from  the  sun's 
rays.  And  it  is  in  the  warm  layer  of  air  so  produced  that 
animals  and  plants  chiefly  flourish.  Ascend  a  mountain's  side 
and  a  height  is  soon  reached  at  which  eternal  snow  and  cold 
prevail,  where  animal  life  cannot  penetrate  and  even  the  low- 
est forms  of  vegetable  life  can  hardly  make  their  residence. 
What  has  thus  far  been  said  points  out  a  valuable  office  of 
water  vapor,  and  one  that  is  entirely  in  addition  to  that 
which  this  same  material  performs  as  it  floats  in  the  clouds, 
ready  to  fall  as  beneficent  showers  and  then  to  proceed  to  the 
other  steps  in  the  progress  of  that  useful  circulation  wrhich  it 
performs  as  a  liquid.  But  it  may  not  be  out  of  place  to 
mention  here  that  the  aqueous  vapor  in  the  atmosphere  ap- 
pears to  serve  in  another  way  for  man's  pleasure,  even 
though  in  this  particular  no  utility  can  be  claimed.  Thus 
the  glories  of  sunrise  and  sunset,  which  have  delighted  intel- 
ligent beings  for  so  many  ages,  are  paintings  upon  the  dra- 
pery of  the  firmament  which  the  pencil  of  light  has  been 
enabled  to  produce  through  the  medium  of  the  refractive 
power  of  those  gathering  drops  of  water  which  float  about 
in  various  forms  and  combinations  in  the  morning  or  the 
evening  sky. 

It  has  already  been  more  than  once  declared  that  carbon 
dioxide  is  poured  out  into  the  atmosphere  by  all  the  ordinary 


THE  ATMOSPHERE.  181 


processes  of  combustion.  This  is  not  only  true  of  combustions 
such  as  those  of  coal  and  wood  and  similar  highly  carbon- 
aceous materials  ;  it  applies  with  equal  force  to  the  animal 
body  itself,  which  has  been  properly  likened  to  a  furnace. 
The  air  taken  into  the  lungs  at  each  breath  inspired  supports 
during  life  a  continual  combustion,  by  reason  of  which 
minute  fragments  of  the  animal  tissue  are  burned  in  all  parts 
of  the  system.  One  of  the  products  of  this  burning  is  car- 
bon dioxide,  which  is  carried  to  the  lungs,  thence  to  be  ex- 
haled as  a  waste  product  into  the  atmosphere.  It  might  at 
first  be  expected  that  this  carbon  dioxide  would  accumulate, 
and  form  a  constantly  increasing  proportion  of  the  air.  But 
it  is  one  of  the  proper  foods  of  vegetable  life  ;  for  nature 
has  wonderfully  provided  that  plants  should  thrive  by  the 
absorption,  or  inhalation,  of  this  particular  gas.  And  so  all 
the  leaves  in  the  forest  are  continually  cleansing  the  air  of 
that  carbon  dioxide  that  living  animals  have  cast  aside  as  a 
useless  thing.  And  by  a  magnificent  alchemy,  the  result  of 
a  wonderful  and  beneficent  plan,  they  turn  this  waste  mat- 
ter of  the  animal  frame  into  food  for  themselves,  and  they 
cast  out  into  the  air  as  their  refuse  that  oxygen  gas  which 
living  animals  demand.  So,  then,  the  two  forms  of  living 
beings  exist  in  a  harmonious  partnership  by  reason  of  which 
each  one  is  benefited. 

An  example  similar  to  that  just  given  with  respect  to  car- 
bon dioxide  is  found  in  ammonia  gas.  This  substance  is  one 
of  the  commonest  products  of  the  decay  and  decomposition 
of  animal  matters.  Wherever  animal  waste  is  deposited  upon 
the  surface  of  the  earth  it  quickly  evolves  ammonia  gas. 
This  gas  diffuses  itself  through  the  atmosphere  under  the  in- 
fluence of  conditions  whereby  it  may  perform  an  important 
service  ;  for  it  is  always  extremely  soluble  in  water.  And  so 
as  soon  as  rain  is  condensed,  whether  in  a  gentle  shower  or 
in  abundant  torrents,  each  drop  in  passing  through  the  air 
gathers  ammonia  and  carries  it  down  to  the  earth.  Again, 
ammonia  is  one  of  the  chief  foods  for  plants.  And  so  the 
rain  drops,  charged  with  such  ammonia  as  they  have  been 


182  CHEMISTRY. 


able  to  collect,  bear  it  to  the  rootlets  in  the  soil  as  a  valuable 
and  important  food,  and  one  which  has  been  proved  to  have 
a  most  stimulating  influence  upon  their  growth. 

There  is  not  opportunity  here  for  discussion  of  the  offices 
and  the  interplay  of  the  other  substances  existing  in  atmos- 
pheric air  ;  they  are  more  local  in  their  effects  and  more 
difficult  to  trace  and  to  describe. 

The  Air  is  not  a  Chemical  Compound. 

The  importance  of  the  atmosphere  and  its  great  abundance 
have  naturally  led  to  most  thorough  scientific  scrutiny  of  it. 
Thus  the  amounts  of  its  principal  constituents  have  been 
studied  with  extreme  care.  One  result  has  been  that  the 
principal  constituents — the  oxygen  and  the  nitrogen— have 
been  found  to  exist  in  air  in  proportions  singularly  constant  in 
amount.  This  fact  has  suggested  to  some  chemists  the  im- 
pression that  air  is  a  true  chemical  compound.  This  latter 
suggestion,  however,  appears  not  to  be  sustained  by  the  most 
rigid  examinations  that  have  been  made.  In  fact  they  give 
ample  support  to  the  opinion  already  declared — that  the  air 
consists  of  a  mass  of  merely  mingled  gases,  and  that  these 
gases  are  uniformly  maintained  in  their  proper  proportional 
amounts  by  the  beautiful  interaction  of  the  physical  and 
chemical  forces  with  which  they  are  endowed. 

Fitness  of  Atmospheric  Air  for  its  Uses. 

The  statements  already  presented  must  have  suggested  to 
the  reader  that  the  atmospheric  air  fulfills  its  offices  in  nature 
much  as  any  contrivance  carefully  devised  by  an  intelligent 
framer  would  accomplish  the  work  for  which  it  was  planned. 
Besides  those  chemical  adaptations  which  have  been  the  prin- 
cipal grounds  upon  which  this  line  of  thought  has  been  sup- 
ported here,  there  are  others  which  may  be  briefly  suggested. 

By  reason  of  the  mobility  of  air,  as  well  as  its  tendencies 
to  expansion  by  heat,  our  atmosphere  is  necessarily  in  a  state 
of  most  intricate  ebbing  and  flowing.  One  prominent  effect 
of  the  motion  thus  set  up  is  to  cause  a  transfer  of  warm  air, 


THE  ATMOSPHERE.  183 

and  so  a  distribution  of  heat,  from  more  favored  portions  of 
the  globe  to  the  others. 

This  same  result  is  also  more  completely  attained  by  the 
influence  of  the  specific  heat  of  air.  Atmospheric  air  has  re- 
markable power — in  which  it  resembles  to  some  extent  water 
— to  take  up  a  very  large  amount  of  heat  with  but  a  slight  rise 
in  temperature  ;  similarly  a  slight  fall  of  temperature  is  asso- 
ciated with  a  large  evolution  of  heat.  By  reason  of  these 
properties  air,  like  water,  has  an  exceptional  storage  power  for 
heat.  This  contributes  largely  to  the  equalization  of  climates. 

The  elasticity  of  the  atmospheric  air  permits  it  to  be- 
come a  useful  servant  of  man  in  the  transmission  of  sound. 
Thus  human  beings — and  with  less  distinctness  most  of  the 
living  creatures  of  the  lower  orders — communicate  their 
thoughts  by  means  of  spoken  words  through  that  line  of  at- 
mospheric air  extending  from  them  to  their  hearer  or  hearers. 

Again,  the  characteristics  of  the  atmosphere  are  such  that  it 
diffuses  sunlight.  By  this  is  meant  that  in  air  sunlight  does 
not  confine  itself  to  those  strictly  straight  lines  which  it  fol- 
lows in  empty  spaces.  So  then  this  property  of  air  mitigates 
the  blackness  of  shadows,  and,  for  example,  he  who  walks  into 
a  shady  lane  does  not  plunge  into  absolute  darkness,  as  he 
might  if  we  were  deprived  of  this  beneficial  diffusing  in- 
fluence of  the  atmospheric  air. 

The  two  considerations  last  adduced  contribute  much 
toward  making  the  earth  a  cheerful  home  for  human  beings; 
for  they  aid  materially  in  the  distribution  of  intelligible  ideas. 
Moreover  those  properties  of  air  by  virtue  of  which  its  un- 
dulating waves  make  music  possible,  and  further  those  which 
permit  the  flight  of  light,  and  so  allow  of  the  existence  of 
the  graphic  arts,  certainly  make  no  mean  contributions  to  the 
happiness  of  man ;  thus  they  help  to  furnish  the  earth  as  his 
place  of  residence. 

READING   REFERENCE. 
Atmosphere,  Selective  power  of,  for  heat  rays. 

— Langley,  S.  P.  Science,  v,  p.  450, 


184  CHEMISTRY. 


XXII. 

EXPLOSIVES. 

IHE  principal  explosives  owe  their  activity,  to  a  very 
large  degree,  to  the  presence  of  nitrogen  in  them  • 
thus  they  may  properly  be  discussed  in  connection 
with  that  element. 
The  explosives  of  chief  importance  are  four  in  number  : 
gunpowder,  the  fulminates,  gun-cotton,  nitroglycerin.  From 
this  list  arises  a  suggestion  of  the  uses  of  these  substances  in 
warfare  ;  but  it  must  not  be  forgotten  that  they  have  also 
important  applications  in  the  arts  of  peace.  Thus,  enormous 
quantities  of  gunpowder  and  nitroglycerin  are  used  in  blast- 
ing operations,  for  purposes  like  the  removal  of  rock  prepara- 
tory to  laying  foundations  for  large  buildings,  as  well  as  in 
excavations  for  railway  cuttings  and  in  the  boring  of  tunnels  ; 
also  in  the  getting  of  building  stone  from  quarries,  the  tear- 
ing of  ore  out  of  mineral  bearing  veins  in  mining  operations  ; 
and  for  loosening  coal  in  coal  pits.  Large  quantities  are 
likewise  employed  in  pyrotechnics.  It  must  not  be  forgotten 
that  fireworks  are  not  only  for  purposes  of  night  illuminations 
and  for  public  gratification  in  times  of  popular  rejoicings ; 
they  are  also  employed  to  a  considerable  extent  for  such  use- 
ful purposes  as  night  signaling  in  connection  with  vessels  at 
sea. 

The  use  of  gunpowder  may  be  mentioned  also  in  its  con- 
nection with  the  life-saving  stations  on  the  sea-coast.  It  is 
a  charge  of  gunpowder  in  a  mortar  that  propels  a  cannon-ball 
having  a  line  attached  to  it  to  a  vessel  in  distress. 

Gunpowder. 

Of  the  various  explosives  mentioned,  gunpowder  is  the 
oldest.  While  the  invention  of  this  substance  has  often  been 
referred  to  Roger  Bacon,  the  celebrated  English  friar  who 


EXPLOSIVES.  185 


died  about  1292,  it  is  now  conceded  that,  though  Bacon  evi- 
dently knew  the  composition  of  it,  the  original  invention  dates 
far  earlier  than  his  times.  There  seems  foundation  for  the  be- 
lief that  it  is  at  least  a  thousand  years  old,  while  its  use  in  artil- 
lery at  the  battle  of  Crecy  shows  its  employment  in  warfare 


FIG.  45.— Roger  Bacon,  born  near  Ilchester,  about  1214 ;  died,  probably  at  Oxford,  in 
1292. 

for  over  five  hundred  years.  Bacon's  power  of  independent 
thought  placed  him  so  far  in  advance  of  the  century  in  which 
he  lived  that  he  became  an  object  of  persecution,  but  he  is 
at  present  ranked  as  one  of  the  prominent  figures  of  history. 
In  his  works  Bacon  refers  to  a  substance  that  seems  to  corres- 
pond to  gunpowder,  and  in  terms  that  suggest  that  he  consid- 
ered it  as  a  material  of  not  uncommon  knowledge  in  his  day. 


186  CHEMISTRY. 


The  principal  constituents  of  gunpowder  are  three:  potassic 
nitrate,  charcoal  and  sulphur.  The  chemical  action  between 
potassic  nitrate  and  charcoal  in  gunpowder  may  be  better 
understood  after  a  simple  experiment,  which  any  one  can  try. 
The  experiment  referred  to  is  as  follows  :  take  a  large  piece 
of  charcoal ;  heat  it  over  a  spirit  lamp  or  gas  lamp  until  cer- 
tain portions  of  it  take  fire  so  as  to  burn  with  a  slight  glow  ; 
next,  sprinkle  very  carefully  a  small  amount  of  powdered 
potassic  nitrate — also  called  both  saltpetre  and  nitre — upon 
the  glowing  part.  A  burning,  something  like  that  of  gun- 
powder, only  less  violent,  results.  The  potassic  nitrate  has 
the  formula  KNO3.  When  it  falls  upon  the  glowing  coal  a 
portion  of  the  oxygen  leaves  the  other  constituents  of  the 
saltpetre  and  accomplishes  thereby  a  true  combustion  of  the 
carbon.  One  important  factor  in  the  operation  is  the  element 
nitrogen  ;  owing  to  the  general  inertness  of  nitrogen  it  easily 
allows  the  escape  of  other  elements  combined  with  it.  So,  in 
case  of  the  experiment  just  suggested,  the  combustion  of  the 
charcoal  is  referable  to  oxygen  liberated  by  reason  of  the 
feeble  affinity  of  one  of  the  other  constituents  of  the  potassic 
nitrate — that  is,  the  nitrogen.  Thus  far  the  only  thing  partic- 
ularly suggested  is  the  combustion  that  takes  place  ;  another 
point  of  importance  may  be  mentioned  in  this  connection. 
If  finely  powdered  charcoal  and  potassic  nitrate  are  thoroughly 
intermingled  and  then  set  on  fire  in  a  closed  vessel,  a  large 
amount  of  gas,  carbon  dioxide,  will  be  generated  by  the  com- 
bustion ;  arid  this  gas  may  burst  the  vessel  unless  it  is  a  very 
strong  one.  If,  however,  the  vessel  has  an  opening  supplied 
with  a  cork  or  plug,  this  stopper  will  be  violently  driven  out 
by  reason  of  the  explosive  force  of  the  carbon  dioxide  gener- 
ated. So,  in  the  preparation  of  gunpowder,  potassic  nitrate, 
charcoal,  and  the  third  substance,  sulphur,  are  finely  pulver- 
ized and  carefully  intermingled.  Thus  they  are  brought  to  a 
state  of  thorough  diffusion  and  intimate  contact.  The  offices 
of  carbon  and  potassic  nitrate  have  been  already  explained. 
The  office  of  the  sulphur  is  principally  to  combine  with  the 
potassium  of  the  potassic  nitrate,  yielding  as  a  result  a 


EXPLOSIVES.  187 


somewhat  larger  evolution  of  gas.  At  all  events,  when  gun- 
powder is  consumed,  two  important  results  are  afforded.  As 
already  intimated,  the  first  is  the  sudden  liberation  of  a  very 
large  amount  of  gas— carbon  dioxide.  The  second  is  that 
this  gas  is  generated  by  a  process  of  true  combustion  attended 
with  great  heat,  the  latter  contributing  largely  to  the  ex- 
plosive force  by  reason  of  the  great  expansion  of  the  gaseous 
products  effected  by  the  heating. 

There  are  several  different  kinds  of  gunpowder,  but  they 
all  consist  essentially  of  the  constituents  mentioned.  Their 
differences  are  either  in  the  proportions  of  the  constituents 
used  or  in  the  size  of  the  granules  in  which  the  powder  is 
formed.  Thus  for  some  war  purposes  it  is  requisite  that  the 
powder  should  burn  very  rapidly,  while  in  others  it  is  required 
to  burn  slowly.  For  the  purpose  of  regulating  the  rate  of 
combustion,  the  grains  are  made  of  various  sizes.  The  smaller 
sizes  burn  more  quickly,  while  those  of  larger  dimensions,  as 
well  as  those  more  strongly  compressed,  burn  more  slowly. 

While  the  exact  chemical  changes  which  take  place  when 
gunpowder  burns  are  too  complicated  to  admit  of  discus- 
sion here,  they  are  in  the  main  those  just  explained. 

Fireworks. 

Gunpowder  affords  the  basis  of  the  pyrotechnic  art.  It  is 
employed  also  with  the  distinct  intention  of  utilizing  both  of 
those  prime  properties  already  referred  to.  That  is  to  say, 
by  reason  of  its  explosive  force,  gunpowder  produces  the  var- 
ious forms  of  motion  and  the  loud  reports  requisite  in  fire- 
works. By  reason  of  the  intense  heat  afforded  by  its  com- 
bustion, the  various  kinds  of  light  are  producible.  The  truly 
marvelous  effects  obtained  by  the  skilled  pyrotechnist  involve 
the  use  of  a  great  multitude  of  substances  and  also  an  ingen- 
ious mechanical  combination  of  them. 

So  many  forms  and  combinations  of  fireworks  are  pos- 
sible that  no  enumeration  can  be  made  here  ;  moreover,  their 
infinite  capabilities  depend  upon  the  inventive  resources  and 
skill  of  the  maker.  In  a  brief  description,  the  rocket  may  be 


188  CHEMISTRY. 


taken  as  the  type  of  fireworks.  It  is  often  of  most  ingenious 
construction.  Thus  it  may  be  provided  with  many  chambers, 
one  connecting  with  another  by  proper  passages.  In  these 
passages  are  placed  fuses  so  that  the  fire  shall  run  from  one 
chamber  to  another  in  proper  order.  Of  course  the  main 
barrel  contains  a  quickly  burning  gunpowder.  This  is  for 
the  purpose  of  producing  the  ascent.  It  is  well  known  that 
a  pistol,  a  rifle  or  a  cannon  always  experiences  a  strong 
recoil  when  fired.  So  does  a  rocket  ;  but  the  rocket  is 
so  constructed  that  the  recoil  is  the  chief  factor  in  its  first 
discharge.  That  is,  in  the  case  of  the  rocket,  the  discharge 
is  downward  and  the  recoil  upward  ;  so  that  in  fact  the 
ascent  of  the  rocket  is  due  to  what  may  be  called  an  ex- 
ceedingly powerful  recoil.  When  the  rocket  is  high  in  air, 
the  fuse  connected  with  its  principal  barrel  lights  its  sub- 
ordinate chambers,  and  these  then  exploding  distribute  into 
the  sky  the  brilliant  masses  of  stars  or  other  graceful  pieces 
originally  intended.  The  loud  reports  that  take  place  at  such 
times  are  due  to  portions  of  violently  explosive  substance 
within  certain  chambers,  while  the  party-colored  lights  pro- 
duced are  referable  to  the  burning  of  substances  which  have 
been  carefully  selected  for  the  purpose.  Thus  the  pyrotech- 
nist has  recourse  to  mixtures  of  gunpowder  and  various  other 
chemical  substances  to  produce  colored  fire.  Finely  powdered 
charcoal  or  lamp-black  give  rise  to  a  red  fire  :  so  also  do  most 
of  the  salts  of  strontium.  Common  salt  or  powdered  resin  give 
rise  to  yellow  fire.  Copper  filings  and  certain  salts  of  copper 
produce  greenish  hues  ;  so  do  salts  of  birium.  Zinc  filings 
and  chloride  of  copper,  and  certain  others,  produce  blue 
shades.  Saltpetre,  in  considerable  quantity,  affords  a  delicate 
pink  ;  while  iron  filings  and  steel  filings  and  magnesium  filings 
produce  scintillations  of  great  brilliancy. 

Fulminates. 

The  fulminates  are  substances  that  are  so  extremely  un- 
stable in  chemical  character  that  they  require  but  a  very 
slight  mechanical  blow  to  decompose  them.  Two  fulminates 


EXPLOSIVES.  189 


in  particular  may  be  mentioned  :  fulminate  of  mercury  and 
fulminate  of  silver.  They  are  both  viewed  as  salts  of  a  pe- 
culiar complex  acid  called  fulminic  acid.  This  acid  is  a  com- 
pound of  carbon,  hydrogen,  oxygen  and  nitrogen.  When 
silver  or  mercury  takes  the  place  of  the  hydrogen  in  fulminic 
acid,  the  dangerous  salts  just  mentioned  are  obtained.  Ful- 
minating mercury  is  the  onu  of  chief  use.  It  is  employed  in 
percussion  caps.  A  drop  of  gum  is  put  in  the  inside  of  the 
cap,  then  the  exact  amount  of  fulminate  in  the  form  of  a 
powder  is  allowed  to  fall  into  the  gum  ;  finally  the  whole  is 
allowed  to  harden.  When  the  cap  is  used,  a  violent  blow 
from  the  hammer  of  the  gun  or  pistol  gives  rise  to  the  ex- 
plosion of  the  fulminate,  and  this  communicates  to  the  gun- 
powder of  the  cartridge  to  be  fired.  Fulminating  silver  is  too 
dangerous  for  use  in  percussion  caps,  but  it  is  employed  in 
certain  explosive  toys  like  torpedoes. 

Gun-cotton. 

Gun-cotton  is  a  chemical  modification  of  the  ordinary 
cotton  fibre.  This  fibre,  when  purified  by  chemical  washings, 
consists  entirely  of  the  substance  called  cellulose,  composed 
of  carbon,  oxygen  and  hydrogen.  It  is  not  different  from 
certain  other  vegetable  fibres. 

When  clean  cotton  is  acted  upon  by  strong  nitric  acid  it 
undergoes  the  wonderful  chemical  change  to  gun-cotton : 
without  material  alteration  in  its  physical  appearance  there 
has  been  a  chemical  substitution  by  reason  of  which  a  nitro- 
gen compound  has  been  introduced  into  the  chemical  mole- 
cule, as  a  substitute  in  place  of  certain  of  the  hydrogen  atoms 
originally  present. 

On  this  account  gun-cotton  is  often  spoken  of  as  trinitro- 
cellulose.  By  reason  of  this  chemical  substitution  the  cot- 
ton changes  as  if  by  magic  from  the  simple,  safe  material 
ordinarily  known,  to  one  of  the  most  dangerous  of  explosives. 
Thus  Mr.  Abel,  the  chemist  to  the  English  War  Department, 
who  has  made  a  series  of  most  careful  studies  of  gun-cotton 
with  reference  to  its  use  for  war  purposes,  finds  the  explosive 


190  CHEMISTRY. 


power  of  gun-cotton  to  be  more  than  fifty  times  that  of  gun- 
powder of  equal  weight.  One  of  the  greatest  objections  to 
the  use  of  gun-cotton  is  found  in  the  fact  that,  upon  keeping, 
it  undergoes  of  itself  a  steady  decomposition  resulting  ulti- 
mately in  dangerous  explosions.  This  fact  appears  to  be 
likely  to  prevent  the  substance  coming  into  general  use. 

Nitroglycerin. 

Glycerin — produced  at  present  in  enormous  quantities  from 
fats  and  oils — is  well  known  as  a  sweetish,  oily  and  harmless 
substance.  Glycerin  is  composed  of  carbon,  hydrogen  and 
oxygen  in  proportions  but  slightly  different  from  those  in 
cotton.  Thus  its  formula  is 

C3HfiO3II3. 

If  this  bland  and  simple  material  is  subjected  to  the  action 
of  concentrated  nitric  acid,  it  undergoes  a  change  very 
similiar  to  that  recognized  in  the  case  of  cotton  as  just  de- 
scribed. It  then  produces  a  compound  called  trinitroglycerin, 
which,  while  it  ranks  as  one  of  the  most  powerful  and  use- 
ful explosives,  it  is  also  associated  with  a  long  list  of  horrible 
disasters  produced  by  accidental,  or  in  some  cases  intentional, 
explosions  of  it. 

Nitroglycerin  is  itself  an  oily  material,  and  it  was  first  con- 
siderably used  in  that  form.  The  terrible  accidents  from 
transportation  of  the  article  have  given  rise  to  the  adoption  of 
two  means  for  lessening  the  risks  attending  it.  The  first  is 
the  manufacture  of  the  substance  in  suitable  localities — that 
is,  near  to  great  public  works  in  which  it  is  to  be  employed. 
And,  again,  the  factories  are  so  arranged  that  the  operations 
of  the  manufacture  shall  be  conducted  in  small  buildings  sur- 
rounded by  earthworks  sufficient  to  localize  any  explosion 
that  might  unhappily  occur. 

At  the  manufactory  of  explosives  at  Ardeer,  on  the  Scotch 
coast,  about  fifty  miles  from  Glasgow,  a  most  ingenious  ad- 
ditional precaution  is  taken.  Here  each  laborer,  as  he  enters 


192 


CHEMISTRY. 


the  works  in  the  morning,  passes  into  a  cottage  to  change  his 
dress.  He  dons  a  uniform  of  a  special  and  distinctive  color 
—it  may  be  scarlet,  or  bright  blue  or  white  or  gray,  accord- 
ing to  the  department  in  which  he  is  employed.  Thus  the 
policemen  who  are  constantly  on  duty  can  detect  at  once  any 
employe  who  strays  into  a  department  to  which  he  does  not 
belong  and  where  his  lack  of  acquaintance  with  the  processes 
might  lead  to  a  terrible  accident. 

Another  special  device  is  the  invention  of  Albert  Nobel, 
who  has  been  noted  as  the  principal  person  by  whose  efforts 
nitroglycerin  has  been  introduced  into  the 
important  uses  which  it  finds  at  the  present 
day.  This  is  the  absorption  of  the  liquid  nitro- 
glycerin in  some  spongy  material,  such  as  will 
serve  as  a  safe  and  proper  vehicle  for  the  ex- 
plosive. The  substance  thus  employed  is  a  kind 
of  fine  silicious  earth  called  diatomaceous  earth, 
also  infusorial  earth.  This  is  a  mineral  material 
found  in  various  parts  of  the  world  in  somewhat 
abundant  deposits.  Upon  examination  by  the 
microscope  it  is  found  to  be  composed  of  the 
mineral  skeletons  of  microscopic  organisms. 
(See  page  252.)  This  substance  by  virtue  of 
its  minute  cellular  texture  seems  to  be  admi- 
rably fitted  to  imbibe  the  liquid  nitroglycerin, 
and  assist  in  packing  it  in  proper  cartridges. 
The  explosive  produced  by  the  combination 

FIG.  47.-Dynamite  js   tne  one  COmmonly  known    as    dynamite.* 
Exploder.  /  ,  \ 

A  peculiarity  of  nitroglycenn  and  dynamite 

is  that  they  cannot  be  fired  in  the  ordinary  fashion.  That 
is,  if  a  lighted  match  is  brought  to  them  they  may  take  fire 
and  burn  with  perfect  quietness.  For  their  explosion  they 
demand  some  kind  of  violent  blow.  For  this  reason  their 
cartridges  have  to  be  provided  with  special  exploders.  These 
are  small  cases  of  gunpowder,  or,  perhaps,  fulminating  mate- 
rials, which  may  be  set  on  fire  by  means  of  a  powder  fuse  or 
*  Dynamite  is  pronounced,  dln'am-lt. 


I 

8 


£ 


EXPLOSIVES.  193 


an  electric  current ;  their  explosion  within  the  nitroglycerin 
mass  determines  a  violent  shock  to  the  latter.  It  is  the  con- 
cussion thus  produced  that  is  the  appropriate  means  of  ex- 
ploding the  nitroglycerin  or  dynamite  cartridges. 

While  sad  accidents  with  these  materials  have  horrified 
the  whole  world  by  their  sudden  and  disastrous  results,  it  is 
too  often  forgotten  that  their  gigantic  forces  are  day  by  day 
safely  and  quietly  contributing  to  the  execution  of  great  pub- 
lic works  all  over  the  earth.  Thus,  in  the  great  rock  tunnels 
of  Mont-Cenis  and  St.  Gothard,  which  pierce  the  Alps,  nitro- 
glycerin and  dynamite  have  done  the  work  of  armies  of  men. 
In  the  St.  Gothard  tunnel  more  than  two  million  pounds  of 
dynamite  have  been  employed,  and  it  has  proved  wonderfully 
effective  in  advancing  most  arduous  subterranean  work. 

Dynamite  has  been  used  with  success  by  Arctic  explorers 
to  open  passages  in  the  ice.  The  following  item,  from  a 
recent  American  Associated  Press  dispatch,  shows  a  similar 
application  of  this  explosive: 

DOVER,  N.  H.,  Feb.  15,  1888.— It  was  expected  by  many 
that  the  railroad  bridge  at  Dover  Point  would  completely 
collapse  with  the  out-going  tide  to-night  by  the  action  of 
the  ice,  but  this  did  not  occur.  Some  very  large  cakes  of 
ice  came  down  to  the  bridge,  one  piece  being  over  500  feet 
long,  but  the  presence  of  thousands  of  smaller  pieces 
about  the  bridge  prevented  it  from  doing  harm.  A  gang  of 
men  has  been  employed  all  the  afternoon  and  evening 
breaking  up  the  ice  field  between  the  bridge  and  Fox  Point, 
a  distance  of  two  miles,  with  dynamite  cartridges,  and 
they  have  been  very  successful. 

An  unsurpassed  illustration  may  be  found  in  the  destruc- 
tion of  Flood  Rock,  in  the  swift  and  dangerous  channel 
called  Hell  Gate,  near  New  York  city.  After  the  failure  of 
many  previous  attempts  to  remove  this  obstruction,  Gen. 
John  Newton,  of  the  U.  S.  Army,  recommended  exploding  it, 
after  thoroughly  tunneling  it  underneath.  The  preparatory 
work  occupied  seventeen  years,  that  is,  from  1868  to  1885. 
Finally  the  drill  holes  in  the  mine  were  supplied  with  their 
cartridges,  more  than  42,000  in  number,  and  weighing  over 
282,000  pounds;  and  on  October  10,  1885,  the  largest 
mass  of  explosives  ever  fired  at  once  performed,  its  office  in 
the  interests  of  commerce  and  industry,  and  Flood  Rock 
13 


194  CHEMISTRY. 


became  a  mere  mass  of  debris,  which  will  gradually  be   re- 
moved by  dredging. 

Unquestionably,  then,  the  principal  use  of  dynamite  is  in 
the  labors  of  peace.  Still,  nitroglycerin  and  dynamite  have 
come  into  great  prominence  by  reason  of  their  use  in  naval 
warfare.  Torpedoes  of  a  great  variety  of  forms  are  now  con- 
structed so  that  a  quick-moving  launch  may  steam  up  to  a 
large  ship  of  war,  place  close  to  her  side  one  of  these  danger- 
ous contrivances,  and  then  quickly  withdraw  in  time  to  avoid 
the  effects  of  the  explosion,  which  involves  the  great  vessel 
in  devastating  ruins.  Torpedoes  charged  with  nitroglycerin 
or  dynamite  are  also  used  for  the  defense  of  harbors,  being 
sometimes  placed  in  such  a  way  that  an  enemy's  ship,  in 
crossing  the  line  formed  by  the  torpedoes,  shall  by  that  act 
explode  one  or  more  of  them  and  produce  her  own  destruction. 


READING  REFERENCES. 

Dynamite,  Manufacture  of. 

La  Nature,  p.  154  (Feb.  4,  1888.) 
Explosive  Agents. 

Abel,  F.  A. — Jour,  of  Chem.  Soc.  of  London,     xxiii,  41,  xxvii,  536. 

— Chem.  News.— xxxix,   165,  187,  198,  208. 
Explosives,  A  New  Class  of. 

Sprengel,  H. — Jour,  of  Chem.  Soc.  of  London,  xxvi,  796. 
Explosives,  Force  of. 

Berthelot. — Annales  de  Chimie  et  de  Physique.  4  Ser.  xxiii,  223. 
Explosives,  in  Blasting. 

Scribner's  Monthly,  iii.  33. 
Explosives,  Literature  of. 

Munroe,  Chas.  E.— Proceedings  of  U.  S.  Naval  Institute,  No,  35 

(referred  to  in  Chem.  News. — liv,  308). 
Explosives,  Use  of,  at  Flood  Rock  (Hell  Gate  N.  Y.) 

Derby,  Geo.  McC. — Sanitary  Engineer,  xiii.  9.  New  York. 
Greek  Fire,  (so  called). 

Lalanne,  L. — Anriales  de  Chimie  et  de  Physique.  3  Ser.  iv,  433. 
Gun-cotton,  Manufacture  and  Composition  of. 

Abel,  F.  A. — Jour,  of  Chem.  Soc.  of  London,  xx,  311,  505. 
Gunpowder,  Chemical  Theory  of. 

Debus,  H.— Chemical  News,  xlv,  91. 


PHOSPHORUS.  195 


XXIII. 

PHOSPHORUS. 


is  a  most  interesting  chemical  ele- 
ment. This  is  because  of  its  exceptional  chemical 
properties,  the  very  important  part  it  plays  in  the 
chemistry  of  animal  and  vegetable  life,  and  its 
employment  in  the  friction  match,  one  of  the  most  conven- 
ient and  useful  articles  of  human  invention. 

Phosphorus  appears  to  have  been  tirst  prepared  in  the 
year  1669  by  a  Hamburg  merchant  named  Brandt,  who  be- 
came fascinated  with  the  study  of  alchemy  and  pursued  his 
experiments  with  the  hope  of  repairing  his  broken  fortunes 
by  the  discovery  of  the  philosopher's  stone.  The  happy 
discovery  of  phosphorus,  while  it  did  not  enrich  him,  at  least 
preserved  his  name  in  the  annals  of  chemistry.  Brandt  pro- 
duced it,  by  a  laborious  process,  from  certain  animal  matters. 
Notwithstanding  the  remarkable  properties  of  the  substance 
and  the  extraordinarily  useful  purposes  to  which  modern 
scientific  knowledge  has  applied  it  and  its  compounds,  phos- 
phorus remained  the  merest  toy  for  more  than  a  hundred 
years.  In  1771  Scheele  revealed  to  the  world  the  fact  that 
it  may  be  prepared  from  bone-ashes  —  that  is  from  burnt  bone 
—  and  this  has  ever  since  been  found  to  be  its  most  conven- 
ient source. 

The  name  phosphorus  is  derived  from  two  Greek  words 
(</>w£  phos,  light,  and,  0epw  pkero,  I  bear)  which  suggest  one 
of  its  marked  properties  ;  namely,  its  power  of  continually 
affording  light,  even  though  not  set  on  fire  after  the  manner 
of  ordinary  illuminating  materials.  It  is  true  the  light  is 
feeble,  and  chiefly  noticeable  in  the  dark.  It  is  the  same,  in 
fact,  as  that  yielded  in  the  dark  by  an  ordinary  friction 
match  when  it  is  gently  rubbed,  but  has  not  yet  taken  fire. 
This  light,  however,  is  the  product  of  a  true  combustion,  only 


196  CHEMISTRY. 


of  a  very  slow  one;  and  again  this  burning  of  phosphorus  is 
initiated  by  heat,  (though  only  a  very  moderate  amount  is 
required  for  it).  Of  course,  for  phosphorus,  much  less  heat 
is  demanded  than  to  set  on  fire  our  ordinary  combustibles. 

Sources  of  Phosphorus. 

Phosphorus,  though  very  widely  distributed  in  nature,  is 
never  found  free  or  uncombined.  This  fact  is  distinctly 
referable  to  the  ease  with  which  the  substance  combines 
with  oxygen  ;  if  it  were  found  free  at  any  point  on  the  sur- 
face of  the  earth  where  it  suffered  exposure  to  atmospheric 
air,  it  would  of  course  quickly  enter  into  combination  with 
oxygen. 

Phosphorus  exists  occasionally  in  the  earth  in  the  state  of 
combination  in  very  hard  rocky  masses,  of  which  the  mineral 
known  as  apatite — composed  mainly  of  calcic  phosphate — 
is  a  good  example.  It  is  also  present  in  small  quantities  in 
almost  all  soils;  and  in  minute  quantities  in  most  natural 
waters,  like  river-water  and  sea-water. 

One  of  the  most  familiar  substances  containing  phosphorus 
is  the  bony  skeleton  of  the  higher  animals.  Here  also  it 
exists  as  calcic  phosphate.  It  exists  also  in  the  brain, 
though  in  a 'form  of  chemical  combination  not  easily  stated. 

Further,  it  is  a  constituent  of  various  portions  of  the  vege- 
table structure,  especially  of  seeds. 

Agricultural  Uses  of  Phosphorus. 

The  statements  in  the  last  two  paragraphs  have  been  pre- 
sented with  the  express  purpose  of  calling  attention  to  the 
important  offices  of  phosphorus  in  connection  with  animal 
and  vegetable  life.  Thus  exact  experiments  have  shown 
that  plants  do  not  flourish  in  soils  barren  of  phosphates,  and 
that  the  mere  addition  of  almost  any  soluble  phosphate 
to  an  arid  soil  promptly  stimulates  the  plant  living  upon 
it  into  more  luxuriant  growth.  These  facts  have  led  to 
the  introduction  into  commerce  of  artificial  fertilizers  con- 


PHOSPHORUS.  19? 


taining  soluble  phosphates  as  their  principal  ingredients  ;  and 
the  manufacture  of  such  fertilizers  has  continually  expanded, 
until  now  it  is  conducted  by  the  principal  commercial  nations 
on  a  truly  gigantic  scale.  For  the  purpose  of  this  manufact- 
ure bones  are  particularly  favorable  because  of  their  poros- 
ity. In  fact,  the  surface  of  the  world  is  ransacked  to  supply 
this  raw  material.  Thus  from  the  deserts  of  Africa  bones 
are  conveyed  as  far  as  England  to  be  manufactured  into 
fertilizers;  and  so  from  the  great  western  plains  of  the  United 
States  bones  are  brought  to  the  eastern  centres  for  a  like  use. 

The  agricultural  demand  for  phosphates  of  some  sort  has 
become  so  imperious  that  even  apatite  is  now  largely  used, 
notwithstanding  the  difficulties  that  its  exceedingly  hard 
and  compact  structure  places  in  the  way  of  the  manufac- 
turer. 

From  the  plant  phosphorus  finds  its  way,  in  the  form  of 
food,  into  the  animal  system.  The  living  animal  appreciates 
this  essential  ingredient,  carefully  selects  it  out  from  the 
food,  and  stores  it  up  both  in  its  brain  and  in  its  bony  frame- 
work. This  framework  is  exceedingly  important  as  giving 
the  requisite  rigidity  to  the  whole  structure,  the  proper  sup- 
port for  the  action  of  the  various  muscles,  and  protection  for 
the  softer  organs. 

Preparation  of  Phosphorus. 

Phosphorus  itself  is  prepared  by  a  process  too  complicated 
for  the  ordinary  amateur  chemist  to  repeat;  indeed,  its  prep- 
aration, even  on  the  large  scale,  presents  serious  difficulties. 
These  are  associated  with  the  great  combustibility  of  the 
substance,  which  makes  necessary  extraordinary  precautions 
against  fire.  Again,  laborers  in  phosphorus  works  are  sub- 
ject to  a  painful  and  incurable  disease  called  phosphorus 
necrosis,  which  has  a  peculiar  and  destructive  effect  upon  the 
bones  of  the  jaw.  Finally,  the  chemical  changes  involved 
give  rise  to  such  difficulties  and  complexities  as  force  the 
manufacturer  to  unusual  watchfulness.  In  fact,  it  has  been 
recently  stated  that  there  are  scarcely  more  than  two  facto- 


198 


CHEMISTRY. 


ries  for  phosphorus  manufacture  in  the  world — one  in  En- 
gland and  one  in  France. 

The  element  phosphorus,  as  ordinarily  seen,  has  much  the 
appearance  of  wax.  It  has  a  white  or  amber  color,  and  is 
translucent;  it  may  be  cut  with'  a  knife  much  as  wax  cuts. 
It  is  ordinarily  sold  in  the  form  of  cylinders  of  about  half  an 
inch  in  diameter.  It  is  necessary  to  keep  it  in  vessels  of 
water,  for,  as  already  stated,  if  exposed  to  the  air  it  would 


FIG.  48.— Coignet's  apparatus  for  production  of  red  phosphorus.  Ordinary  phos- 
phorus is  placed  in  a  cast-iron  vessel  c ;  it  is  then  heated  ten  or  twelve  days,  an  even 
temperature  being  maintained  by  the  two  iron  jackets,  one  inclosing  sand,  the  other 
holding  fusible  alloy. 

oxidize.  This  oxidation,  at  first  slow,  increases  in  vigor  from 
the  heat  afforded  by  the  portions  oxidized  first.  After  a 
short  exposure  to  air  a  stick  of  phosphorus  spontaneously 
bursts  into  flame.  Evidently,  then,  phosphorus  should  not 
be  handled  except  under  water.  Cases  are  recorded  of 
severe  and  even  fatal  burns — the  result  of  handling  phos- 
phorus in  the  air. 

We  may  with  propriety  call  attention  here  to  another 
peculiarity  of  phosphorus,  which  constitutes  one  of  the  re- 
markable features  of  this  interesting  element.  About  thirty- 
five  years  ago  a  Vienna  chemist,  von  Schrotter,  discovered 


PHOSPHORUS.  190 


that  when  phosphorus  is  heated  for  a  considerable  length  of 
time,  under  conditions  such  that  no  gas  is  present  which  can 
act  chemically  upon  it,  it  undergoes  a  marked  change  in  its 
properties.  Thus  its  color  turns  to  red,'  and,  strange  to  say, 
it  loses  altogether  that  ready  combustibility  which  is  the 
most  striking  characterstic  of  ordinary  phosphorus.  It  may 
seem  incredible  that  any  such  change  could  in  fact  occur. 
But  this  red  phosphorus  has  become  an  article  of  considerable 
importance  in  commerce,  and  it  is  a  well-established  fact  that 
ordinary  phosphorus  may  be  turned  into  this  modification 
without  any  gain  or  loss  of  weight,  and  that,  on  the  other 
hand,  this  red  phosphorus  may  be  turned  back  again,  by 
suitable  processes,  to  the  ordinary  form,  also  without  gain 
or  loss  of  weight.  Phosphorus  is  not  the  only  elementary 
substance  that  is  capable  of  this  kind  of  change.  Indeed, 
the  general  term  allotropism  has  been  applied  to  the  tendency 
of  elementary  substances  to  undergo  internal  changes,  by 
reason  of  which  their  chemical  properties  are  temporarily 
modified  without  gain  or  loss  of  weight,  and  therefore  inde- 
pendently of  chemical  combination  or  decomposition.  (See 
page  121.) 

Chemical  Properties  of  Phosphorus. 

The  chemical  properties  of  phosphorus  are  wide  in  their 
range — that  is,  it  combines  with  many  of  the  chemical 
elements.  Thus  it  unites  with  hydrogen  in  several  pro- 
portions, and  thereby  forms  several  compounds,  called  phos- 
phuretted  hydrogen.  As  might  be  expected,  they  are  all  ex- 
ceedingly combustible  ;  one  of  them,  in  particular,  takes  fire 
at  ordinary  temperatures  immediately  upon  coming  in  con- 
tact with  the  atmosphere.  Its  production  affords  opportunity 
for  a  beautiful  experiment,  though  a  somewhat  dangerous  one. 
When  the  gas  is  produced  in  a  retort  it  may  be  made  to 
bubble  through  water  in  the  form  of  vapor  in  company  with 
various  other  gases  generated  at  the  same  time.  Then,  as  it 
reaches  the  surface,  it  instantly  takes  fire,  the  phosphorus 
burning  to  a  white,  smoke-like  substance  which  usually  floats 


200  CHEMISTRY. 


away  in  forms  similar  to  those  of  smokers'  rings.  The 
smoke  consists  of  minute  particles  of  a  solid,  called  phos- 
phorus pentoxide,  and  expressed  by  the  formula  P2O5.  This 
is  evidently  the  product  of  the  combustion  of  that  phos- 
phorus which  is  a  part  of  the  inflammable  gas.  The  shape  of 
the  rings  is  due  to  a  mere  mechanical  circumstance,  and  the 
same  in  effect  as  that  afforded  by  the  lips  of  the  smoker  while 
producing  rings.  Indeed,  if  a  paper  box,  having  a  round  hole 


FIG.  49.— Phosphuretted  hydrogen  gas,  of  tbe  spontaneously  Inflammable  variety, 
taking  fire  in  air  and  forming  smoke-rings. 

on  one  side,  be  filled  with  smoke  of  any  kind,  sharp  blows 
upon  the  opposite  side  will  drive  out  portions  of  the  smoke 
in  such  a  way  as  to  produce  similar  rings.  Such  rings  are 
often  seen  on  a  still  day  puffed  out  of  the  smokestack  of  a 
locomotive,  and  they  are  sometimes  produced  by  the  dis- 
charge of  a  cannon  in  still  air.  The  fact  is  that  in  all  these 
cases  the  portion  of  smoke  producing  a  ring  advances  through 
the  opening  with  a  sudden  impulse,  the  edge  of  the  opening 
retarding  those  particles  that  pass  nearest  to  it.  Thus  the 
delayed  particles  acquire  a  tendency  backward  and  inward 
which  starts  them  on  the  peculiar  series  of  circular  courses, 
which  in  the  grand  aggregate  gives  rise  to  the  rings. 

As   has  more   than  once   been  stated,  phosphorus   has   a 
marked  affinity  for  oxygen.     It  burns  in  any  vessel  contain- 


PHOSPHORUS.  201 


ing  air,  combining  with  oxygen  in  such  a  way  as  to  readily 
deprive  the  air  of  the  entire  amount  of  this  element  contained 
in  it. 

The  chemical  change  is  represented  by  the  following 
equation : 

P2  -f  5O2  2PaOs 

One  molecule  of  Five  molecules  of  Two  molecules  of 

Phosphorus,  Oxygeu,  Phosphorus  pentoxide, 

124  160  284 

parts  by  weight.  parts  by  weight.  parts  by  weight. 

V y 1  V ^ > 

284  284 

When  the  operation  is  performed  in  a  tall  jar  the  oxide 
of  phosphorus  produced  falls  as  abundant  flakes  having  a 
snow-like  consistency.  When  these  flakes  are  thrown  upon 
water  they  chemically  combine  with  the  water,  affording 
much  heat  and  producing  a  hissing  sound  which  is  the 
evidence  of  it.  The  liquid  now  acquires  a  sour  taste,  refer- 
able to  the  fact  that  phosphoric  acid  has  been  produced. 

The  chemical  change  is  represented  by  the  following 
equation  : 


P205             + 

3H20       = 

2H3P04 

One  molecule  of 

Three  molecules  of 

Two  molecules  of 

Phosphorus  pentoxide, 

Water, 

Phosphoric  acid, 

142 

54 

196 

parts  by  weight. 

parts  by  weight. 

parts  by  weight. 

196  196 

Phosphoric  acid  is  the  starting-point  of  an  immense  series 
of  salts  called  phosphates.  One  of  these,  calcic  phosphate,  we 
have  already  referred  to  as  existing  in  bones  and  in  apatite. 

Friction  Matches. 

The  earliest  method  of  producing  flame  appears  to  have 
been  by  the  friction  of  pieces  of  dry  wood  in  contact  with 
dry  leaves  or  similar  combustible  substances.  This  method 
travelers  have  found  to  be  still  in  use  among  tribes  of  a  low 
stage  of  development.  The  next  method  seems  to  have  been 


202  CHEMISTltY. 


by  the  use  of  flint  and  steel  and  tinder.  When  the  flint  is 
sharply  struck  against  the  steel  it  tears  off  minute  particles 
of  the  metal,  and  these  fragments  are  heated  to  the  luminous 
point  by  the  violence  of  the  stroke  ;  if  they  are  made  to  fall 
upon  the  tinder  this  easily  combustible  material  takes  fire; 
from  its  burning  a  candle  or  lamp  may  be  lighted.  But  the 
flint  and  steel  and  tinder  must  be  dry  and  in  good  order,  to 
produce  the  best  results ;  even  then  considerable  skill  is  de- 
manded. So  it  is  easy  to  see  that  mankind  has  often  pre- 
ferred to  preserve  aflame  once  lighted^  and  then  communicate 
this  to  another  and  another  from  time  to  time,  rather  than  to 
go  to  the  trouble  of  exciting  a  new  combustion  when  fire  was 
needed.  And  it  is  easy  to  appreciate  the  usefulness  to  its 
possessor  of  a  flame  once  kindled — and  the  serious  incon- 
venience resulting  from  its  extinction.  Thus  we  can  readily 
comprehend  how  some  nations  have  adopted  fire  as  a  deity  to 
be  worshiped,  and  considered  it  worthy  to  be  preserved  con- 
tinuously unextinguished,  and  to  be  guarded  with  religious 
care. 

The  flint  and  steel  method  has  ample  illustration  as  to  its 
principle,  not  only  in  familiar  cases  like  sparks  from  the 
horse's  hoof,  but  also  in  many  processes  in  factories  and 
machine-shops.  Here  it  is  well  known  that  the  grindstones 
used  for  finishing  articles  of  iron  and  steel  send  off  from  their 
work  an  uninterrupted  current  of  minute  chips  of  the  hot 
and  luminous  metal. 

This  method  of  obtaining  fire  held  its  own  until  about 
sixty  years  ago.  In  1829  a  kind  of  chemical  match  was  de- 
vised, and  soon  after,  in  1832,  a  true  friction  match  containing 
phosphorus  was  brought  into  use.  The  principles  upon  which 
the  phosphorus  match  depends  are  but  very  slightly  different 
from  those  involved  in  the  use  of  the  flint  and  steel.  Thus  in 
the  ordinary  friction  match  the  rubbing  upon  the  rough  sur- 
face is  a  mechanical  process  which  generates  heat,  just  as  any 
blow  or  any  friction  does.  In  the  case  in  question  the 
amount  of  heat  is  small,  but  it  is  sufficient  to  set  on  fire  the 
small  amount  of  phosphorus  on  the  tip  of  the  match  ;  the 


PHOSPHORUS. 


phosphorus  sets  on  fire  the  sulphur  which  coats  over  the  end 
of  the  match  ;  the  sulphur  in  burning  sets  on  fire  the  wood 
of  the  match,  and  here  the  combustion  has  reached  a  stage  at 
which  it  is  easily  communicated  to  larger  masses  of  material. 
In  the  finer  kinds  of  wooden  matches,  in  order  to  avoid  the 
objectionable  smell  of  burning  sulphur,  this  latter  substance 
is  sometimes  replaced  by  a  thin  coating  of  wax  upon  the  end 
of  the  stick.  In  this  case  other  chemicals  are  added  to  the 
tip  of  the  match,  in  order  to  make  the  combustion  more 
active. 

Friction  matches  of  the  ordinary  kind  are  now  so  abundant 
and  familiar  every- where  that  the  exceeding  usefulness,  con- 
venience and  importance  of  the  match  as  a  device  or  in- 
vention  is  apt  to  be  overlooked.  It  is  not  intended  to  dwell 
here  upon  this  subject,  however,  for  perhaps  what  has  been 
said  of  the  appliances  for  lighting  used  in  the  past,  renders 
unnecessary  further  presentation  of  the  principles  utilized  in 
the  little  tapers  of  to-day. 

As  an  article  of  manufacture  the  individual  match  is  so 
small  that  it  is  not  easy  at  first  to  appreciate  the  greatness 
of  the  commercial  interest  it  represents.  Thus  it  is  estimated 
that  in  Europe  alone  fifty  thousand  persons  are  constantly 
employed  in  the  manufacture  of  the  various  kinds  of  matches. 
Again,  though  the  amount  of  phosphorus  used  in  each  match 
is  very  minute,  its  sum  total  is  no  less  than  a  thousand  tons 
a  year.  The  value  of  the  annual  product  of  this  industry  is 
not  far  from  fifty  millions  of  dollars. 

If  there  were  introduced  here  an  account  describing  at 
length  the  manufacture  of  the  friction  match — commencing 
at  the  beginning,  with  the  special  kind  of  wood  employed  and 
the  processes  used  for  its  subdivision  into  the  requisite  frag- 
ments, continuing  even  so  as  to  explain  the  various  contriv- 
ances for  packing  the  finished  product — that  description 
might  be  of  interest  ;  but  the  special  topic  seems  to  be  more 
properly  the  preparation  and  application  of  the  material  at 
the  tip  of  the  match.  The  sticks  having  been  prepared, 
they  are  placed,  by  machine,  in  frames  capable  of  containing 


204  CHEMISTRY. 


large  numbers  of  them.  They  are  first  sulphured — that  is, 
their  ends  are  dipped  in  melted  sulphur  and  it  is  allowed  to 
harden  upon  them.  For  the  finer  grade  of  matches,  however, 
the  sulphur  must  be  dispensed  with,  and  instead  the  sticks 
are  dipped  into  melted  wax. 

In  any  case,  they  are  next  tipped  with  the  highly  inflam- 
mable material,  this  process  being  called  chemicking.  The 
inflammable  paste  is  prepared  in  large  quantities  by  mixing 
the  proper  ingredients  in  a  kettle  surrounded  by  boiling 
water.  First,  a  solution  of  an  appropriate  gum  or  glue  is 
made.  When  it  has  attained  a  proper  consistency,  the 
phosphorus  is  introduced  little  by  little.  The  whole  mass  is 
then  slowly  but  thoroughly  agitated  with  a  wooden  stirrer 
until  the  phosphorus  is  diffused  through  the  mass.  Finally, 
other  ingredients,  such  as  potassic  nitrate  or  binoxide  of  lead 
or  manganese  dioxide,  which  favor  combustion,  are  added  ; 
and  certain  coloring  matters,  such  as  Prussian  blue  or  ver- 
milion, are  introduced.  Here  is  a  German  recipe  for  making 
this  paste  : 

Gum,  16  parts. 

Phosphorus,  9  parts. 

Potassic  nitrate,  14  parts. 

Manganese  dioxide,  16  parts. 

As  has  already  been  intimated,  all  of  these  substances, 
except  the  phosphorus,  may  be  replaced  by  others,  according 
to  the  style  of  the  article  to  be  manufactured  or  the  views  of 
the  maker.  The  process  of  chemicking  consists  in  dipping 
the  sulphured  ends  into  the  inflammable  paste,  which  for  this 
purpose  is  spread  out  on  a  stone  slab.  Finally,  the  tips  are 
coated  over  with  a  thin  varnish  to  protect  them  from  absorp- 
tion of  moisture. 

At  present  the  manufacture  of  friction  matches  is  carried 
on  to  a  very  large  extent  in  Sweden,  and  that  country,  it  is 
now  stated,  produces  about  seventy-five  per  cent,  of  all  the 
matches  made  in  the  world.  In  Sweden,  too,  are  largely 
manufactured  what  are  called  safety  matches.  The  safety 
matches  are  tipped  with  a  composition  of  potassic  chlorate, 


PHOSPHORUS. 


205 


potassic  dichromate,  red  oxide  of  lead,  and  sulphide  of  anti- 
mony. Under  ordinary  circumstances  friction  will  not  set 
these  matches  on  fire.  In  lighting,  they  must  be  rubbed  on 
a  prepared  surface  which  contains  principally  red  phosphorus 
and  sulphide  of  antimony.  When  the  match  is  rubbed  upon 
this  surface,  the  postassic  chlorate  of  the  match  and  the  red 
phosphorus  of  the  friction-surface  start  a  chemical  combi- 
nation which  extends  to  the  other  materials  on  the  tip  of 
the  match.  Safety  matches,  then,  involve  an  invention 
which  in  accomplishing  its  purpose  affords  a  twofold  advan- 


FIG.  50.— Pan,  or  water-bath,  for  melting  and  mixing  the  inflammable  paste  for 
match  tips. 

tage.  In  the  first  place,  as  the  match  lights  only  on  the  pre- 
pared surface,  the  danger  of  conflagrations  from  accidental 
ignition  of  them  is  very  largely  reduced.  This  costly  feature 
of  the  ordinary  phosphorus  match  would  be  largely,  if  not 
entirely,  done  away  with  by  general  use  of  the  safety  match. 
In  the  second  place,  the  use  of  red  phosphorus  has  the  advan- 
tage of  saving  human  lives.  Thus  it  spares  the  operatives 
employed  in  this  business  the  liability  to  the  phosphorus 
disease  already  mentioned.  Again,  ordinary  phosphorus  is 
very  poisonous ;  in  fact  the  tips  of  matches  containing  this 
substance  have  not  only  often  produced  the  death  of  children 


206  CHEMISTRY. 


who  have  tasted  them,  but  such  matches  have  occasionally 
been  used  in  cases  of  intentional  suicide.  Of  course,  as  safety 
matches  contain  no  phosphorus,  these  forms  of  poisoning 
cannot  arise  from  them. 

A  flame  of  fire,  as  a  visible  and  tangible  thing,  has  in  all 
ages  been  accepted  as  a  symbol  which  appropriately  typifies 
enlightenment  of  the  mind  and  soul.  This  favorite  and 
beautiful  figure  loses  none  of  its  fitness  when  narrowed  in  its 
application  to  the  aspects  of  these  subjects  in  their  peculiarly 
modern  forms.  For  in  the  friction  match,  whose  cheapness 
brings  it  to  the  hand  of  every  human  being,  however  low  his 
degree,  we  may  discover  the  type  of  that  opportunity  for  en- 
lightenment offered  to  individuals  whose  circumstances  seem 
most  humble  and  even  forbidding.  The  one  is  the  invention 
of  modern  science ;  the  other  the  gift  of  modern  laws,  of 
modern  theories  of  the  rights  of  men,  of  modern  schools, 
libraries,  and  newspapers,  of  the  modern  printing-press, 
telegraph,  and  railroad. 


READING  REFERENCES. 
Friction  Matches. 

Schrotter,  A.  v.— Chem.  News,     xxxvi,  207,  219,  259. 
Picaud,  A. — La  Nature,  Jan.  1888.  p.  90. 

(This  article  makes  the  distinct  claim  that  the  friction  match  was  in- 
vented in  1831,  by  a  Frenchman  named  Charles  Sauria.) 


CARBON. 


207 


xxiv. 


CARBON. 

ARBON  exists  in  nature  in  a  multitude  of  forms. 
It  is  rarely  found  in  the  absolutely  pure  and  un- 
combined  condition,  though  certain  well-known 
substances  possess  it  in  large  quantity. 


Ordinary  Charcoal. 

Probably  the  most  familiar  and  representative  form  of 
carbon  is  that  known  as  charcoal.  But  charcoal  is  rarely  free 
from  other  chemical  elements,  and  a  distinction  ought  to  be 


FIG.  51.— Charcoal  pit. 

made  between  it  and  the  absolutely  pure  form  of  carbon. 
Charcoal  is  produced  by  the  partial  decomposition  of  vegeta- 
ble or  animal  substances  under  the  influence  of  heat.  Thus 
charcoal  is  commonly  prepared  by  piling  wood  into  a  conical 
heap,  then  covering  it  with  earth  and  sods,  and  finally  set- 


208 


CHEMISTRY. 


ting  it  on  fire  within.  Certain  portions  of  the  wood  are  thus 
burned,  while  others  are  only  charred.  The  wood  is  decom- 
posed by  the  heat  to  which  it  is  subjected  ;  volatile  materials 
generated  by  this  decomposition  are  expelled,  while  there  is 
left  behind  a  solid  matter  consisting  mainly  of  carbon,  and 
called  charcoal. 


FIG.  52.— Charcoal  burners  at  work. 

Animal  Charcoal. 

The  same  general  treatment  of  certain  animal  matters, 
such  as  waste  leather,  gives  rise  to  a  finer  kind  of  carbon 
called  animal  charcoal. 

Again,  when  bones  are  partly  burned  they  produce  what 
is  called  bone-coal.  The  mineral  matter  of  the  bone  under- 
goes no  change  by  the  heat;  but  the  gelatinous  matters 


CARBON. 


200 


which  permeate  it  are  decomposed,  and  they  leave  behind 
them  the  carbon  deposited  upon  this  mineral  matter. 

Lamp-black. 

Another   material,  closely   assimilated    to    those   already 
spoken  of,  is  lamp-black.     This  is  a  product  of  the  imperfect 


FIG.  53.— Manufacture  of  lamp-black. 

combustion  of  substances  like  oil,  tar,  resin,  and  the  like, 
which  are  very  rich  in  carbon.  The  tar,  or  resin,  being  set  on 
fire  is  allowed  to  burn,  but  in  an  imperfect  way,  and  so  as  to 
evolve  a  dense  black  smoke.  The  smoke  flows  into  a  cham- 
14 


FIG.  54.— Tree  trunks  discovered  in  coal  mines. 
(210) 


CARBON. 


211 


ber  prepared  for  it,  where  the  sooty  material  collects  on  the 
floor  and  walls.  It  is  afterward  scraped  up  and  put,  into 
packages  for  commercial  distribution.  In  the  English 
method  of  manufacture  of  lamp-black  the  smoke  is  made  to 
pass  through  a  series  of  heavy  canvas  bags.  From  openings 
at  the  bottoms  of  the  bags  the  soot  is  afterward  drawn  out 
for  packing. 

Coal. 

Anthracite  coal  and  bituminous  coal  are  both  well-known 
compounds  of  carbon.     Anthracite  seems  to  be  derived  from 


FIG.  55.— Bags  in  which  lamp-black  is  collected  in  the  English  process  of  manu- 
facture. 

bituminous  coal  which  has  been  subjected  in  the  earth  to 
heat  and  pressure  under  conditions  favorable  to  the  expulsion 
of  some  of  the  more  volatile  constituents  of  the  original 
bituminous  coal.  Both  of  these  combustibles,  when  care- 
fully studied,  show  distinct  evidences  of  their  vegetable 
origin.  Plainly  they  are  accumulated  masses  of  the  remains 
of  a  rank  vegetation  which  flourished  in  an  earlier  period  in 
the  geological  history  of  our  globe.  Careful  observations 
made  in  the  mines  have  revealed  in  the  coal  the  existence  of 


212  CHEMISTRY. 


trunks  of  trees,  branches,  leaves,  fruits,  in  various  conditions 
from  the  one  extreme  of  comparatively  perfect  preservation, 
to  the  other  extreme  in  which  the  mineral  preserves  a  mere 
impression  of  the  original  vegetable  matter.  These  remains 
have  made  it  possible  to  construct  a  complete  botany  of  this 
period  of  geological  history  ;  and  with  but  a  moderate  aid  of 
the  imagination  artists  have  been  able  to  produce  ideal  land- 
scapes representing  these  early  forms  of  vegetable  life  as 
they  flourished  in  the  ancient  ages. 

Graphite. 

Closely  allied  to  anthracite  coal  is  that  valuable  material 
called  graphite.  This  a  very  compact  and  comparatively 
pure  form  of  carbon.  It  is  familiarly  known  to  every  one  in 
the  black  material  used  in  lead-pencils.  Graphite  is  com- 
monly called  black  lead,  though  it  is  a  well-established  fact 
that  it  contains  none  of  the  metal  properly  called  lead. 
Strangely  enough,  graphite  is  remarkably  incombustible 
under  all  ordinary  circumstances.  It  is  also — like  other 
forms  of  carbon — infusible  even  at  the  highest  temperatures 
known.  On  account  of  these  properties  graphite  finds  use, 
though  it  must  be  deemed  a  somewhat  anomalous  one,  in  the 
manufacture  of  crucibles.  When  the  precious  metals  are 
fused  in  such  a  crucible,  at  a  high  temperature  in  a  glowing 
furnace,  an  interesting  paradox  is  furnished.  It  is  this  :  the 
coal — freely  burning  in  the  fire,  and  so  furnishing  the  intense 
heat  desired — is  fundamentally  of  precisely  the  same  chemi- 
cal nature  as  the  graphite  of  the  crucible,  which  resists  the 
heat  and  combustion,  and,  while  allowing  the  metals  to  melt, 
preserves  them. 

The  Diamond. 

The  diamond  is  nearly  pure  carbon,  crystallized.  Perhaps 
it  is  not  too  much  to  say  that  it  is  the  most  striking  and 
wonderful  of  all  the  forms  of  this  interesting  element.  The 
costliness  of  the  diamond  is  referable  largely  to  its  great 


214 


CHEMISTRY. 


rarity  ;  for  it  is  found  in  comparatively  few  portions  of  the 
earth. 

The  ancient  Greeks  and  Romans  highly  prized  the  rare 
and  precious  crystal,  which  they  obtained  from  India,  and  it 
was  worn  by  them  not  only  because  of  its  costliness  and 
beauty,  but  also  because  they  believed  that  it  served  as  a 


FIG.  57.—"  The  Star  of  the  South."       Fir,.  58.—"  The  Regent "  or  "  Pitt. 


FIG.  59.—"  The  Orloff."  FIG.  60.—"  The  Grand  Mosul." 

Great  diamonds  of  the  world  (natural  size). 

potent  charm  against  alarms  and  enchantments ;  more  im- 
portant yet,  they  ascribed  to  it  the  power  of  preserving  the 
peace  and  harmony  of  the  family  circle.  Upon  this  point  a 
French  writer  has  wittily  said  :  "  Cette  derniere  vertu,  je 
crois  qu'il  la  possede  encore  qnand  le  mari  est  assez  riche 
pour  acheter  le  bijou  que  sa  femme  ambitionne  de  porter  !  " 
The  East  Indies,  the  Brazils  and  the  Cape  of  Good  Hope 
may  be  said  to  be  the  principal  sources  of  this  gem.  In  Bra- 
zil the  search  for  diamonds  is  systematically  conducted.  The 


v ,&-  *  ^sc, 


FIG.  61. -Transportation  of  diamonds  under  military  protection. 
(215) 


216  CHEMISTRY. 


diamond-bearing  soils  are  carefully  pulverized  in  vessels  of 
water,  under  the  direction  of  experienced  inspectors.  The 
work  is  done  by  slaves  who  prosecute  their  search  under  the 
stimulus  of  the  well-understood  rule  that  he  who  finds  a 
diamond  weighing  seventeen  and  one  half  carats,  or  more, 
publicly  receives  his  freedom  as  a  reward.  Notwithstanding 
the  systematic  labor  applied  to  the  search  for  these  gems,  and 
the  fascination  naturally  attending  undertaking's  of  this  sort, 
the  wealth  of  Brazil  is  derived  to  a  vastly  greater  extent 
from  its  agricultural  products  than  from  its  mines.  Thus  it 
is  stated  that  from  1740  to  1822,  a  period  of  more  than 
eighty  years,  the  diamond  mines  yielded  but  little  more  than 
$17,000,000.  On  the  other  hand,  the  value  of  coffee  exported 
in  a  single  year  has  sometimes  been  double  or  even  more 
than  double  this  amount.  Thus  in  the  year  1859  the  coffee 
exported  was  valued  at  above  $28,000,000  ;  and  in  1873  the 
quantity  of  this  article  exported  was  valued  at  above 
$60,000,000. 

In  1728  diamonds  were  discovered  in  Brazil,  and  until  re- 
cently this  has  been  the  chief  source  of  them.  But  in  1868 
a  child  at  play  on  the  banks  of  the  Orange  River,  in  South 
Africa,  picked  up  an  attractive  pebble  which  proved  upon 
examination  to  be  a  diamond  of  twenty-one  and  one  quarter 
carats.  This  accidental  discovery  has  led  to  the  most  im- 
portant results;  for  the  South  African  mines  of  the  great 
Kimberly  district  have  since  yielded,  in  the  aggregate, 
diamonds  valued,  after  cutting,  at  about  five  hundred  mill- 
ions of  dollars. 

The  larger  gems  are  always  exceedingly  rare.  On  this 
account  the  money  value  of  diamonds  increases  in  a  far  more 
rapid  ratio  than  the  weight. 

The  Cutting  of  Diamonds. 

The  cutting  of  diamonds  as  an  art  ha^s  been  known  for  but 
a  few  centuries,  and  the  perfection  with  which  it  is  at  present 
conducted  is  of  much  more  recent  date.  Of  course  the  proc- 


FIG.  62.— Diamond  cutter  at  work. 
(217) 


218  CHEMISTRY. 


ess  is  an  extremely  delicate  and  important  one,  because  it 
involves  splitting  off  portions  of  the  gem  so  as  to  reduce  it 
to  the  exact  geometrical  shape  previously  decided  upon. 
That  form  called  the  brilliant  is  the  one  most  often  produced 


FIG.  63— Diamond  known  as  "  The  Star  of  the  South,"  before  and  after  cutting. 

at  the  present  day.  The  business  of  cutting  diamonds  has 
been  for  a  long  time  concentrated  in  the  city  of  Amsterdam, 
in  Holland.  Here,  among  a  Jewish  population  of  twenty- 
eight  thousand  persons,  ten  thousand  are  employed  exclu- 
sively in  working  on  diamonds.  In  many  cases  diamonds  are 


CARBON. 


210 


subject  to  a  very  large  relative  loss  of  weight  by  the  process 
of  cutting.  Thus  the  Koh-i-noor,  when  brought  from  India 
as  a  gift  from  the  East  India  Company  to  the  English  Crown, 
was  in  a  rough  state  and  weighed  one  hundred  and  eighty- 
six  carats;  it  was  afterward  cut  in  Amsterdam;  it  suffered  a 


FIG.  04.— Diamond  polisher  at  work. 

loss  of  weight  variously  stated  at  from  eighty  to  one  hundred 
carats.  After  the  first  trimming  the  gem  is  carefully  pol- 
ished by  rubbing  it  gently  against  a  revolving  plate  upon 
which  is  a  mixture  of  oil  and  diamond  dust. 

Up  to  the  close  of  the  last  century  the  nature  and  compo- 
sition of  the  diamond  had  been  a  subject  of  interesting 
discussion  among  students  of  natural  science.  At  the  period 


220  CHEMISTRY. 


mentioned,  however,  the  question  was  settled  by  Lavoisier 
and  other  scientific  investigators,  who  clearly  proved  that 
the  diamond  underwent  complete  combustion  in  oxygen  and 
that  as  a  result  carbon  dioxide  gas  was  generated. 


FIG.  65.— The  Koh-i-noor  before  cutting.       FIG.  66.— The  Koh-i-noor  after  cutting. 

Infusibility  of  Carbon. 

Carbon  differs  from  most  solid  substances  in  the  fact  that 
it  is  infusible  at  the  highest  temperature  to  which  it  has  yet 
been  subjected.  And  since  in  the  elementary  form  it  has  not 
been  changed  to  the  liquid  state,  much  less  has  it  been 
brought  to  the  gaseous  condition.  Indeed  this  stability  and 
fixedness  of  carbon  is  one  of  its  most  valuable  attributes. 
Thus  this  characteristic  is  a  principal  one  that  renders  it 
specially  appropriate  for  use  in  the  points  employed  in 
electric  lighting.  It  is  true  these  pencils  slowly  burn  away. 
But  some  combustion  ought  to  be  expected  when  it  is  re- 
membered that  the  electric  current,  flowing  from  one  pencil 
to  the  other,  affords  an  intense  heat  as  well  as  brilliant 


CARBON. 


light.  But  it  is  a  general  law  that  substances  give  out  the 
most  intensely  brilliant  white  light  when  they  neither  liquefy 
nor  volatilize,  and  to  this  principle — exemplified  both  by  the 
carbon  pencils  of  the  so-called  arc  light  and  by  the  delicate 


FIG.  67.— Magnified  view  of  the  carbon  terminals  used  for  the  production  of  the 
electric  light. 

thread-like  carbon  loops  of  the  incandescent  electric  light- 
must  be  referred  not  only  the  brilliancy  of  the  electric 
light,  but  also  in  fact  the  light  produced  by  most  of  our 
illuminating  materials. 


222 


CHEMISTRY. 


Decolorizing  Power  of  Carbon. 

Carbon,  whether  in  the  form  of  wood  charcoal,  animal 
charcoal,  or  bone-coal,  lias  a  wonderful  power  of  decolor- 
izing liquids.  Even  more  compact  carbonaceous  matter,  such 
as  anthracite  coal,  possesses  this  same  property,  though,  as 

might  be  expected,  to  a  much 
interior  degree.  Thus  if  a 
colored  solution  is  strained 
through  a  considerable  quan- 
tity of  one  of  these  forms  of 
carbon,  the  latter  substance 
absorbs  the  coloring  matter 
and  the  liquid  passes  through 
practically  colorless.  On  ac- 
count of  this  wonderful  pow- 
er bone-coal  is  used  in  the 
arts  in  enormous  quantity  in 
many  processes  where  liq- 
uids must  be  decolorized. 
The  sugar  refining  industry 
affords  a  prominent  example 
upon  this  point.  Here  enor- 
mous quantities  of  bone  coal 
are  used  for  the  purpose  of 
whitening  the  syrups  before 
crystallizing  the  sugar. 

Charcoal  has  also  a  similar, 
and  yet  more  striking,  prop- 
erty of  absorbing  offensive 
gases.  Thus  tainted  meat 
packed  in  freshly-burned  charcoal  quickly  loses  its  odor — 
which  is  absorbed  by  the  coal — and  the  meat  then  becomes 
sweet  and  wholesome. 

Chemical  Properties  of  Carbon. 

The  chemical  properties  of  carbon  are  by  no  means  less 
wonderful  than  the  characteristics  already  referred  to.  It  is 


FIG.  66.— Automatic  regulator  whereby 
the  carbon  pencils  of  the  electric  light  are 
maintained  at  the  proper  distance  apart. 


CARBON. 


223- 


very  inert  at  low  temperatures  ;  but  at  high  temperatures 
it  manifests  chemical  activities  of  extraordinary  vigor.  Thus 
at  high  temperatures  carbon  withdraws  oxygen  from  almost 
every  other  element  known,  in  this  way  manifesting  chemical 
force  superior  to  that  possessed  by  any  of  them. 

Other  Natural  Forms  of  Carbon. 

In  addition  to  the  well-known  forms  of  matter  containing 
carbon,  and  already  described,  there  are  yet  many  others. 

Thus  it  is  found  in  the  at- 
mosphere, as  has  already  been 
explained,  in  the  form  of  car- 


bon dioxide.  This  gas  exists 
in  the  air  in  small  relative  pro- 
portions, but  in  enormous  ag- 
gregate amount. 

As  a  natural  carbonaceous 
substance,  petroleum,  too, 
ought  not  to  be  forgotten. 
This  wonderful  and  useful 
substance,  stored  up  beneath 
the  surface  of  the  earth  in 
incredibly  large  quantities, 
owes  its  chief  value  to  its 
wealth  of  carbon.  It  is  com- 
posed of  carbon  and  hydro- 


gen,   but   the    former    is    the    im 


constituent  to  which  is  refer- 
able the  beautiful  light  it 
affords. 


FiCr.  60.— Colored  liquid  filtered  through 
charcoal,  and  thereby  decolorized. 


In  some  petroleum-producing  regions,  notably  in  the  vicin- 
ity of  Pittsburg,  Pa.,  the  earth  contains  pockets  of  gaseous 
hydrocarbons.  These  pockets  have  been  pierced  by  boring 
implements,  and  the  gas,  which  comes  out  under  a  tremendous 
pressure,  is  now  utilized  not  only  for  domestic  heating,  but 
also  in  the  great  manufacturing  establishments  of  that  vi- 
cinity. 


-  - 


CARBON.  225 


Again,  the  marble  and  the  limestones  of  the  globe  contain 
enormous  quantities  of  carbon.  These  minerals  consist 
principally  of  calcic  carbonate  (Ca  CO3)  ;  and  the  carbon 
makes  up  about  one  eighth  of  this  substance.  Since  some 
whole  mountain  chains  consist  chiefly  of  limestone  or  marble 
it  is  plain  that  the  total  amount  of  carbon  in  these  forms 
must  be  very  large. 

Carbon  in  Animal  and  Vegetable  Substances. 

With  few  exceptions,  all  animal  and  vegetable  matters 
contain  carbon,  which  indeed  appears  to  perform  its  most  im- 
portant offices  in  connection  with  the  kingdoms  of  life.  Thus 
it  has  been  called  the  characteristic  element  of  animal  and 
vegetable  compounds.  So  vast  is  the  variety  of  these  com- 
pounds already  recognized  that  it  is  hardly  conceivable  that 
man  can  ever  be  able  to  acquire  an  acquaintance  with  all 
those  as  yet  undetected. 


READING  REFERENCES. 

Coal,  and  the  Coal-mines  of  Pennsylvania. 

Harper's  Magazine,     xv,  451. 
Diamonds. 

Scribner's  Monthly,     v,  529. 

Harper's  Magazine,     xix,  466;  xxxii,  343. 
Diamond  Fields  of  South  Africa. 

Harper's  Magazine,     xlvi,  321. 
Diamonds,  Large. 

Science,     x,  69. 
Petroleum. 

Peckhani,  S.  F. — Report  on    petroleum  in  connection  with  the  U.  S. 

Census  of  1880.     Washington  1885. 
15 


CHEMISTRY. 


XXV. 

COMPOUNDS  OF  CARBON  AND  OXYGEN. 

1HILE  compounds  of  carbon  and  hydrogen  are  very 
numerous,  those  already  known  being  numbered 
by  hundreds,  the  affinities  of  oxygen  and  carbon 
give  rise  to  a  strikingly  different  result. 
When  combined  with  oxygen  alone,  carbon  forms  but  two 
compounds.      These  are  expressed  by  the  following  names 
and  formulas : 

Carbon  monoxide,  CO.  Carbon  dioxide,  C02. 

Carbon  Monoxide  (CO). 

This  gas  is  most  familiarly  known  as  that  one  which  often 
plays  upon  the  surface  of  a  hard  coal  fire  and  burns  there 
with  a  dark  blue,  feebly  luminous,  flame.  Most  of  the  phe- 
nomena of  its  production  and  final  burning  may  be  presented 
as  follows  :  When  an  ordinary  coal  fire,  burning  in  a  stove, 
is  amply  supplied  with  air  at  the  bottom,  the  oxygen  of  the 
air  burns  the  lower  portions  of  carbon  into  carbon  dioxide. 
Next,  this  carbon  dioxide  is  carried  up,  by  the  draft,  between 
any  masses  of  fresh  coal  that  may  be  upon  the  top  of  the 
fire.  This  fresh  coal  has  itself  affinity  for  oxygen  under  the 
circumstances  just  described  as  prevailing.  As  a  result,  each 
molecule  of  carbon  dioxide  from  the  lower  portion  of  the 
fire  yields  one  of  its  atoms  of  oxygen  to  an  atom  of  carbon 
in  the  upper  part. 

The  chemical  change  is  represented  by  the  following  equa- 
tion : 

CO2  +  C  2CO 

One  molecule  of                                       One  atom  of  Two  molecules  of 

Carbon  dioxide,                                Carbon,  Carbon  monoxide, 

44                                               12  56 

parts  by  weight.  parts  by  weight.  parts  by  weight. 

56  56 


COMPOUNDS   OF  CARBON  AND    OXYGEN.         227 

.  —  .-    .  .  * 

As  a  result,  therefore,  carbon  monoxide  is  formed,  and  es- 
capes as  a  colorless  gas  from  the  top  of  the  fuel  ;  there,  if 
the  upper  door  of  the  stove  admits  a  sufficient  amount  of  air, 
the  carbon  monoxide  combines  with  the  oxygen  of  this  air, 
and  burns  with  the  blue  flame  already  referred  to,  and  so 
produces  carbon  dioxide  again. 

This  chemical  change  is  represented  by  the  following 
equation  : 

2CO  +  O2  2CO2 

Two  molecules  of  One  molecule  of  Two  molecules  of 

Carbon  monoxide,  Oxygen,  Carbon  dioxide, 

56  32  88 

parts  by  weight.  parts  by  weight.  parts  by  weight. 


88  88 

The  carbon  monoxide  is  a  very  poisonous  gas,  far  more  in- 
jurious to  health  than  carbon  dioxide. 

Carbon  Dioxide  (CO2). 

This  substance  and  its  manner  of  production  have  been 
referred  to  more  than  once  in  preceding  chapters.  A  some- 
what more  extended  notice  of  it,  however,  is  appropriate  to 
this  place. 

It  has  already  been  stated  that  carbon  dioxide  exists  ready- 
formed  in  nature  —  notably  in  the  atmospheric  air.  Its  prin- 
cipal natural  source  in  the  atmosphere  is  the  combustion  of 
fuel  ;  for  almost  all  fuel  is  carbonaceous.  Thus  coal,  wood, 
oil,  illuminating  gases,  are  all  highly  carbonaceous  substances, 
and  one  of  the  principal  products  of  their  combustion  is  the 
gas  now  under  consideration. 

As  has  already  been  described,  the  respiration  of  animals 
is  closely  connected  with  a  real  combustion  in  the  living 
being.  It  is  true  that  this  sort  of  combustion  is  not  attended 
by  the  evolution  of  light  ;'  it  is  productive  of  heat,  neverthe- 
less, and  the  heat  afforded  by  respiration  is  an  important  fac- 
tor in  the  sustenance  of  animal  existence.  For  this  heat  not 
only  enables  the  living  being  to  endure  the  chilling  effects  of 


CHEMISTRY. 


the  winter's  cold  ;  it  also  keeps  the  temperature  of  the  in- 
ternal organs  up  to  that  point  which  is  necessary  for  the 
proper  performance  of  certain  animal  functions — of  which 
digestion  is  a  most  important  example.  Now  by  this  com- 
bustion carbon  dioxide  is  generated  just  as  truly  as  would  be 


FIG.  71.— Production  of  carbon  dioxide  by  combustion  of  a  diamond  in  oxygen  gas. 

the  case  if  the  flesh  of  the  living  animal  were  consumed  in  a 
glowing  fire.  The  product  of  respiratory  combustion  is  the 
same  carbon  dioxide  as  that  recognized  in  well-defined  burn- 
ings. The  quantities  of  carbon  dioxide  evolved  by  man 
and  certain  of  the  domestic  animals,  in  each  hour  of  their 
existence,  have  been  calculated.  They  are  approximately 
Stated  in  the  following  table  : 


COMPOUNDS  Off  (JAR&6N  AND  OXY&EN.        220 

A  man  exhales  4  gallons  carbon  dioxide  per  hour. 
A  dog         "      4i     "  "  "       "         » 

A  horse      "     50       "  "  "       "         " 

An  ox         "     70       •'  "  "       "         " 

And  M.  Boussingault  has  calculated  that  the  approximate 
amount  of  carbon  dioxide  produced  in  the  city  of  Paris  dur- 
ing a  single  twenty-four  hours  is  as  follows  : 

Amount  produced  by  living  animals 55,000,000  cubic  feet. 

Amount  produced  by  burning  of  various  kinds 

of  fuel 27,000,000  cubic  feet. 

Total  C02  produced  in  twenty-four  hours,  82,000,000  cubic  feet. 

There  are  certain  other  natural  sources  of  carbon  dioxide 
that  are  worthy  of  passing  mention.  Thus  in  many  parts  of 
the  world  the  gas  is  continually  evolved  not  only  from  active 
volcanoes,  but  also  from  extinct  ones.  Again,  another  inter- 
esting source — though  not  in  the  aggregate  a  very  impor- 
tant one — is  found  in  natural  mineral  springs.  In  these  the 
water  often  comes  to  the  surface  highly  charged  with  carbon 
dioxide,  and  the  gas,  escaping  into  the  air,  imparts  to  the 
water  its  well-known  bubbling  appearance.  (See  pp.  139,  142.) 

Experiments  with  Carbon  Dioxide. 

For  chemical  purposes  carbon  dioxide  is  commonly  pro- 
duced by  the  action  of  an  acid  upon  some  one  of  the  salts 
known  as  carbonates.  Accordingly  hydrochloric  acid  and 
calcic  carbonate  (that  is,  common  marble)  when  brought  to- 
gether produce  carbon  dioxide.  This  fact  may  be  readily 
shown  by  the  performance  of  a  simple  but  interesting  ex- 
periment. The  operation  may  also  serve  for  the  display  of 
some  of  the  principal  properties  of  the  gas. 

The  experiment  in  question  may  be  conducted  advantage- 
ously somewhat  as  follows  :  Provide  two  convenient  glass 
jars — such  as  candy  jars  or  preserve  jars ;  also  a  short  candle, 
a  piece  of  copper  wire,  a  bottle  of  hydrochloric  acid  and  some 
fragments  of  white  marble.  Now  attach  the  candle  to  the 


330  CHEMISTRY. 


wire  and  after  lighting  the  former  let  it  down. into  the  jars, 
still  burning.  The  combustion  continues  because  the  jars  are 
full  of  air  and  contain  ample  quantities  of  oxygen.  Next 
withdraw  the  candle  and  extinguish  it  for  a  moment.  Now 
place  in  the  bottom  of  the  larger  jar  some  hydrochloric  acid 
and  into  it  gently  drop  some  of  the  fragments  of  marble. 
Effervescence  immediately  commences.  A  careful  examina- 
tion of  effervescence  shows  that  in  this,  as  in  other  cases,  the 
process  consists  in  the  evolution  of  a  gas  from  a  liquid.  In 
the  case  in  question  a  colorless  gas  is  plainly  evolved,  and 
this  gas  is  carbon  dioxide. 

The   chemical   change   is   represented   by   the    following 
equation  : 


CaCO3      -f      2HC1 

CO2      -f      CaCl2 

-f      H20 

One  molecule  of 

Two  molecules  of 

One  molecule  of 

One  molecule  of 

One  molecule  of 

Calcic  carbon- 

Hydrochloric 

Carbon 

Calcic 

Water, 

ate, 

acid, 

dioxide, 

chloride, 

100 

73 

44 

111 

18 

parts  by  weight. 

parts  by  weight. 

parts  by  weight. 

parts  by  weight. 

parts  by  weight. 

173  173 

After  allowing  the  effervescence  to  continue  for  five  or 
ten  minutes,  relight  the  candle  and  again  lower  it  into  the 
jar  now  containing  carbon  dioxide.  If  a  sufficient  quantity 
of  the  gas  is  present,  the  light  will  be  promptly  extinguished 
when  the  wick  passes  below  the  surface  of  the  gas.  The  ex- 
periment displays  at  this  stage  the  additional  fact  that  the 
carbon  dioxide  is  heavy,  and  in  filling  the  jar  it  does  so  from 
the  bottom  upward.  Now  relight  the  candle  and  immerse  it 
in  the  second  jar ;  this  is  proved  to  contain  air  by  the  fact 
that  the  candle  continues  to  burn.  While  it  is  still  quietly 
burning  there,  pour  gently  upon  it  the  carbon  dioxide  accu- 
mulated in  the  other  jar.  If  the  amount  of  this  gas  is  large 
enough,  it  will  fill  the  jar  containing  the  lighted  candle  and 
so  will  readily  extinguish  the  latter. 

These  experiments  demonstrate  simply  and  clearly,  certain 
of  the  most  important  properties  of  carbon  dioxide.  Its 


COMPOUNDS   OP  C ARSON  AND   OXYGEtf.         231 

action  in  extinguishing  flame  is  to  quench  it,  very  much  as 
water  would.  When  the  candle  dips  beneath  the  surface  of 
the  carbon  dioxide,  the  flame  expires  simply  from  lack  of  that 
oxygen  of  the  air  which  ordinarily  supports  the  combustion. 
And  this  leads  very  naturally  to  the  additional  statement  that, 
in  similar  fashion,  living  beings  are  drowned  if  immersed 
in  carbon  dioxide.  For  just  as  water  prevents  the  access 
of  air  to  the  lungs,  and  then  drowning  ensues,  so  when  the 
animal  is  beneath  the  surface  of  carbon  dioxide  he  dies 
because  the  heavy  gas  acts  as  an  effectual  barrier  to  the 
access  of  air. 

Effervescing  Beverages. 

A  large  quantity  of  carbon  dioxide  taken  into  the  lungs  is 
promptly  fatal  to  animal  life  ;  even  a  small  increase  of  that 
gas,  in  the  atmospheric  air  breathed,  produces  a  marked  low- 
ering of  the  vitality.  It  is  an  interesting  fact,  however,  that 
when  this  gas  is  taken  into  the  stomach,  especially  in  its 
solution  in  water,  it  has  a  wholesome  and  stimulating  effect. 

When  carbon  dioxide  is  dissolved  in  water  it  seems  to  pro- 
duce a  true  acid,  though  an  unstable  one.  In  accordance 
with  the  present  nomenclature,  this  acid  is  called  carbonic 
acid  and  is  represented  by  formula  H2CO3.  This  substance 
is  present  as  the  main  constituent,  or  as  a  subordinate  one, 
in  certain  natural  mineral  waters,  and  in  many  simple  effer- 
vescent beverages.  Thus  plain  soda-water  is  merely  a  so- 
lution of  carbon  dioxide  in  water.  Such  solutions  are  now 
manufactured  on  a  large  scale,  and  by  mechanical  appliances 
are  filled  into  siphon-like  bottles  in  such  a  way  that  small 
quantities  of  the  liquid  may  be  withdrawn  without  loss  of  the 
principal  stock  of  gas. 


232  CHEMISTRY. 


XXVI. 

ORGANIC    CHEMISTRY. 

[HEMISTS  long  ago  recognized  certain  differences 
between  the  substances  found  in  distinctly  ani- 
mal and  vegetable  matters,  on  the  one  hand,  and 
the  substances  found  in  mineral  mutters,  on  the 
other;  between  those  things  which  constitute  organisms 
like  animals  and  plants,  as  compared  with  those  of  non-living 
substances  like  clay,  iron-rust,  alum,  saltpetre,  etc. 

Animal  matters  and  vegetable  matters  are  the  products  of 
bodies  possessing  organs.  Organs  are  parts  having  specific 
functions.  Thus  the  stomach  is  an  organ  possessing  the 
function  of  digestion,  and  the  lungs  are  organs  possessing  the 
function  of  respiration.  Again,  the  leaves,  the  flowers,  the 
seeds,  the  roots,  of  plants,  are  separate  organs,  and  they 
possess  special  and  very  different  functions  of  the  living 
vegetable  to  which  they  belong.  Accordingly,  substances 
derived  from  vegetables  and  animals  are  called  organic. 
Non-living  objects,  as  rocks  and  other  mineral  and  earthy 
substances,  do  not  possess  organs,  and  they  have  long  been 
called  inorganic. 

This  division  of  matters  into  organic  and  inorganic  was  for- 
merly thought  an  essential  one ;  it  is  not  now  considered  so. 
It  is  now  known  that  the  chemical  changes  of  living  animals 
and  plants  are  governed  by  the  same  laws  as  those  prevailing 
in  the  changes  of  rocks  and  other  lifeless  forms  of  matter. 

Grounds  for  Dividing  Chemistry  into  Two  Great 
Departments. 

Chemistry  is  still,  however,  commonly  divided  into  the  two 
great  departments — inorganic  chemistry  and  organic  chemis- 
try ;  but  this  division  is  recognized  as  a  matter  of  con- 
venience mainly. 


ORGANIC   CHEMISTRY.  233 

Three  reasons  which  may  be  mentioned,  why  the  dis- 
tinction is  still  maintained,  are  : 

First.  The  number  of  organic  compounds  is  very  great. 

Second.  These  compounds  perform  varied  and  important 
offices  in  connection  with  human  beings  in  their  growth  and 
nourishment  in  health,  and  in  their  treatment  in  illness.  The 
importance  which  they  assume  is  increased  by  the  relations  of 
the  lower  animals  and  the  individuals  of  the  vegetable  king- 
dom to  man. 

Third.  As  will  appear  hereafter,  the  processes  of  analysis 
and  methods  of  investigation  in  organic  compounds  are 
slightly  different,  as  a  whole,  from  those  that  .serve  for  the 
study  of  inorganic. 

Definition  of  Organic  Chemistry. 

The  inorganic  and  the  organic  worlds  are,  however,  so 
closely  allied  in  some  respects,  and  certain  of  the  substances 
of  the  one  have  such  close  and  natural  affiliations  with 
those  of  the  other,  that  indeed  it  is  often  found  difficult  to 
determine  where  shall  be  placed  the  line  of  demarkation 
between  these  two  great  natural  groups.  In  fact,  chemists 
have  not  found  the  definition  incidentally  introduced  in  the 
preceding  paragraph  sufficiently  distinct.  To  make  it  more 
so,  organic  chemistry  has  been  sometimes  called  the  chemis- 
try of  the  carbon  compounds.  It  has  sometimes  been  called 
the  chemistry  of  the  hydrocarbons.  Again,  the  following  still 
more  rigid  and  scientific  statement  is  often  employed : 
organic  chemistry  includes  those  compounds  in  which  the 
atoms  of  carbon  are  directly  united  either  icith  other  atoms  of 
carbon,  or  with  atoms  of  hydrogen,  or  with  atoms  of  nitrogen. 

Two  Classes  of  Organic  Compounds. 

There  is  one  distinction  between  the  classes  of  organic 
compounds  themselves  that  ought  not  to  be  omitted  here. 
The  members  of  the  organic  family  differ  very  much  in  their 
properties,  according  as  they  are  crystalline  or  cellular. 
Crystalline  organic  compounds,  of  which  cane  sugar  may  be 


234  CHEMISTRY. 

taken  as  a  familiar  and  suitable  example,  are  numerous. 
These  compounds  are  closely  allied  in  some  respects  to  inor- 
ganic compounds.  They  do  not  seem  to  have  so  close  a  re- 
lation to  the  vital  processes  as  might  at  first  be  supposed. 
But  those  organic  compounds  that  are  cellular,  such,  for  ex- 
ample, as  the  fibre  of  wood  and  the  fibre  of  lean  meat,  are 
much  removed  from  inorganic  bodies,  and  seem  to  bear  a 
peculiar  and  close  relation  to  the  vital  forces. 

The  Great  Number  of  Organic  Compounds. 

The  vast  number  of  organic  compounds  is  referable  to  at 
least  four  fundamental  principles  : 

First.  The  chief  element,  carbon,  has  a  large  number  of 
points  of  attraction — that  is,  four;  on  this  account  it  is  capable 
of  attaching  to  itself  by  chemical  affinity  many  other  atoms. 

Second.  Carbon  atoms  are  capable  of  uniting  together  in 
chains  of  great  length  and  variety  of  arrangement.  Two 
methods  of  arrangement  are  especially  noteworthy ;  the  one 
method  is  that  where  the  chains  are  open — that  is,  not  at- 
tached at  the  ends.  The  other  arrangement  is  that  where 
the  chains  are  closed,  the  series  of  atoms  of  carbon  making 
a  circuit.  An  appropriate  example  of  this  style  of  union  is 
found  in  the  benzol  ring  or  the  benzol  hexagon. 

The  open  chain  may  be  conveniently  represented  by  the 
left-hand  diagram  below,  and  the  closed  chain,  the  benzol 
ring,  is  often  represented  by  the  right-hand  diagram  below. 

^ 

~G-  -C*   ^C- 

~~(?~~  — G  C— 

x  c 

I 

Third.  One  of  the  most  interesting  and  important  features 
of  organic  compounds  is  that  in  them  certain  elements  may 


ORGANIC   CHEMISTRY.  235 

stay  together  for  a  considerable  time  in  comparatively  per- 
manent groups  which  act  like  elements.  Such  groups  of 
atoms  are  called  compound  radicles. 

Fourth.  It  is  now  distinctly  recognized  that  a  given  organic 
compound,  possessing  a  certain  distinct  set  of  properties,  may 
have  its  atoms  undergo  a  rearrangement  without  any  increase 
in  the  number  of  them  or  any  change  in  their  kinds  or  rela- 
tive proportions. 

Some  organic  substances  have  molecules  capable  of  several 
different  rearrangements,  such  that  different  compounds  may 
be  produced.  Thus  Professor  Cayley  has  computed  that  a 
compound  of  the  paraffin  group  containing  four  carbon  atoms 
is  capable  of  two  rearrangements  within  the  molecule ;  but  a 
compound  of  this  group  containing  thirteen  carbon  atoms  is 
capable  of  as  many  as  seven  hundred  and  ninety-nine  dif- 
ferent rearrangements  of  its  atoms.*  This  property  of  or- 
ganic compounds  is  called  isomerism. 

Organic  Radicles  Act  like  Elements. 

It  has  already  been  pointed  out  that  the  seventy  recognized 
elements  are  capable  of  interaction  and  combination  to  pro- 
duce a  vast  number  of  compounds. 

Now  the  compound  radicles  of  organic  chemistry,  espe- 
cially the  hydrocarbons,  act  like  so  many  more  elements, 
and,  being  themselves  far  more  numerous  than  the  true 
elements,  these  compound  radicles  afford  the  material  which 
may  be  combined  into  yet  larger  numbers  of  substances  than 
those  recognized  among  inorganic  matter. 

The  inorganic  compounds  have  been  arranged  in  a  certain 
order  in  accordance  with  their  natural  affiliations,  and  though 
when  such  arrangement  is  made  some  gaps  appear,  these 
gaps  are  of  great  service  in  that  they  suggest  that  many 
more  compounds  than  those  yet  recognized  or  described  may 
be  hereafter  produced. 

*  Cayley,  *'  On  the  analytical  forms  called  trees,  with  applications,  the  theory  of  chem- 
ical combinations."  Brit.  Assoc.  Rep.  1875,  257.  Recalculated  by  Dr.  Hermann,  of 
Wurtzburg.  (Referred  to  in  Roscoe  &  Schorlemmer's  Chemistry,  vol.  iii.  Part  I.  p.  122). 


236  CHEMISTRY. 


To  the  organic  compounds  the  same  statement  may  be 
applied.  Gaps  in  their  list  point  out  an  avenue  for  future 
discovery  in  organic  chemistry. 

Organic  Compounds  Classified. 

The  difficulty  of  classifying  organic  compounds  is  of  course 
very  great.  This  is  duej€/t>^,  to  their  great  number;  second, 
to  the  many  relationships  of  one  and  the  same  substance; 
third,  to  the  relative  imperfection  of  our  acquaintance  with 
the  most  of  them.  Those  substances  with  which  chemists 
are  best  acquainted  are  arranged  for  discussion  in  many  dif- 
ferent ways.  The  following  outlines  will  serve  to  indicate 
the  form  in  which  the  subject  is  briefly  presented  in  this 
chapter : 

First. — The  great  group  of  substances  derived  from  marsh 
gas,  and  called,  in  general,  the  open-chains  or  paraffin  or 
fatty  series. 

Second. — The  great  group  of  substances  derived  most  di- 
rectly from  benzol,  and  called  in  general  the  closed-chain  or 
aromatic  series. 

Third. — Other  less  easily  classified  vegetable  matters. 

Fourth. — Other  less  easily  classified  animal  matters. 

Sub-Chapter  I.— The  Fatty  Series. 
This  great  group  includes  many  compounds  of  both  practi- 
cal and  theoretical  interest.  They  are  best  understood  by  a 
tabular  statement  based  on  what  is  called  type-compounds. 
This  may  be  presented  as  follows  (these  types  moreover 
serve  also  for  the  aromatic  series,  with  slight  modifications) : 

Types  of  Organic  Compounds, 
ist  Type,      H— H,      The  Hydrogen-gas  Type. 

The  general  formula  is  R — R. 

+ 

R  represents  one  molecule  of  an  electro-positive  radicle. 


ORGANIC  CHEMISTRY.  237 

It  may  be  either  simple  or  compound.     When  compound,  it 
is  usually  made  up  of  carbon  and  hydrogen. 

R  represents  one  molecule  of  an  electro-negative  radicle. 
It  may  be  either  simple  or  compound.  When  compound,  it 
is  usually  made  up  of  carbon,  hydrogen  and  oxygen. 

EXAMPLES. 

C+    + 
R— R    Positive  radicle    CH3— CH3     Methyl, 

1   R— R    Negative  radicle     C2H30— C2H30     Acetyl, 

I  R— R    Ketone-      CH3— C2H30    or   0=C=(CH3)2       Ordinary  acetone 

(methyl-acetyl). 

R— H    Hydride        CH3— H    Methyl  hydride  (marsh-gas), 
R— H     Aldehyd        C2H30— H     Acetic  aldehyd, 

R— €1  C2H5— Cl     Etliyl  chloride, 

(Halogen  substitution  compound) 
R— Cl  C2H30— Cl    Acetyl-chloride. 


2d  Type,    H2O,  or  H— O— H,    The  Water  Type. 

The  general  formula  is  R — D — K.     D  represents  one  atom 
of  a  linking  dyad.     It  is  usually  oxygen. 
M  represents  one  atom  of  a  monad  metal. 

EXAMPLES. 

-f          4- 

R— 0— R  Simple  ether  C2H5— 0— C2H5     Ethylic  ether, 

+  + 

R— 0— R  Mixed  ether  CH3— 0— C2H5     Methyl-ethyl-ether, 

R— 0— R     Anhydride  C2H30— 0— C2H30     Acetic  anhydride, 

+ 

R— 0 — R     Compound  ether        C2FT5 — 0 — C2H30     Ethyl-acetic  ether, 

R_O— H    Alcohol  C2H6— 0— H     Ethyl  alcohol, 

+ 

R— S — H     Mercaptan  C2H5— S — H     Ethyl  sulpho-hydrate, 

R — Se — H    Seleno-mercaptan     C2H6 — Se — H    Ethyl  seleno-hydrate, 
H— 0— R~    Acid  H— 0— C2H30     Acetic  acid, 

M— 0— ¥    Salt  Na— 0— Cj,H30    Sodic  acetate. 


238 


CHEMISTRY. 


R— N=: 


3d  Type,     H3N,    The  Ammonia-gas  Type. 
EXAMPLES. 

I3     Amine  C2H5 — N=H3     Ethyl-amine, 

(CH3)3  As  Tri-methyl-arsine, 
(C2H5)3  Sb  Tri-ethyl-stibine, 
C2H5 — P=H2  Ethyl-phosphine, 


R  —  As=H3     Arsine 

+ 

R—  Sb=H2     Stibine 

+ 

R  —  P=H2     Phosphino 

=H2     Amide 


_ 


Ztr     Alkalamide,        C3H6— NZH 


C2H30  —  N=H2     Acet-amide, 
C2H30 


Ethyl-acet-amide, 


TT7-0-H 


R''     «     ;i      Amic  acid  (CO)"  Carbamic  acid. 

—  i>  =  r!2  —  IN  =  r!2 

+  ^v 

R4  _  N  —  Cl   Ammonium  subs,  comps.  (C2H5)4^N  —  01    Ethyl-ammonium 

chloride, 
4-  —  :v 

R4  _  P  —  01  Phosphon  him  subs,  comps.  (CH3)4=P—  01  Tetra-methyl  plios- 

phonium  chloride. 
+       v 

R4=As  —  01  Arsonium  substitution  compounds. 
+  =v 
R4z=rSb  —  01   Stibonium  substitution  compounds. 

A  few  of  the  compounds  of  carbon  with  hydrogen  are  pre- 
sented in  the  following  table.  They  represent  mere  starting- 
points,  so  to  speak,  of  an  immense  number  of  derivatives. 


Parafins. 

Olefines. 

Acetylenes. 

Methane  CH4 

Ethane,     02H6 

Ethylene,  C2H4 

Acetylene,  C2H2 

Propane,  C3H8 

Propylene,  C3H6 

Allylene,  C3H4 

Butane,     C4H10 

j  Butylene,  C4H8        ) 
t  Tsobutylene,  C4H8  J 

Crotonylene.  C4H6 

Pentane,  C5H12 

j  Pentylene,  C5H10  ) 
I  Amylene,  C5H10    J 

Yalerylene,  CBH8 

Hexane,    C6HM 

Hexylene,  C6H,2 

Hexoylene,  C6Hi0 

Heptane,  C7H16 

j  Heptylene,  C7H14        ) 
I  Isoheptylene,  C7H14    j" 

Oenanthylidene,  C7Hi2 

Marsh  gas  is  found  in  water  in  swampy  places,  where, 
under  the  influence  of  heat  and  moisture,  vegetable  matters 
are  undergoing  decomposition.  The  gas  rises  in  bubbles 


ORGANIC  CHEMISTRY.  239 

which  are  capable  of  taking  fire  from  a  lighted  match.  It 
has  been  analyzed  and  found  to  have  the  composition  H4C, 
already  stated. 

By  the  replacement  of  its  hydrogen  atoms,  wholly  or  partly, 
by  other  atoms  or  radicles,  the  carbon  compounds  of  the 
fatty  series  are  produced. 

The  hydrocarbons  of  this  series  have  their  most  striking 
natural  source  in  petroleum,  an  oil  flowing  from  the  earth  by 
natural  or  artificial  openings,  especially  in  certain  parts  of 
America,  Europe  and  Asia. 

The  hydrocarbons  of  this  (and  other)  series  are  artificially 
produced  from  coal  in  the  manufacture  of  illuminating  gas, 
a  chemical  industry  which  is  discussed  more  at  length  in  a 
later  chapter. 

Chloroform  is  produced  when  bleaching  powder  is  warmed 
with  ordinary  alcohol  (called  ethyl  alcohol).  The  substance 
has  a  sweetish  odor  and  has  the  remarkable  though  well- 
known  property  of  producing  insensibility  to  pain.  Owing, 
however,  to  the  danger  of  death  from  overdose,  chloroform 
is  going  out  of  use  as  an  anaesthetic — ether,  ethyl  ether,  which 
is  much  safer,  replacing  it.  The  chemical  formula  of  chloro- 
form (CH  C13)  at  once  reveals  its  chemical  relationship  to 
marsh  gas  (CH4). 

Compounds  of  Carbon,  Hydrogen  and  Oxygen. 

In  the  table  already  given  reference  has  been  made  to  alco- 
hols, ethers,  aldehydes,  and  acids.  Each  of  these  terms,  at 
first  applying  to  a  special  substance,  is  now  applied  to  a  class 
of  substances.  Thus  there  are  many  alcohols;  there  are  many 
ethers  ;  there  are  many  aldehydes  ;  there  are  many  acids. 

A  volatile  liquid  called  wood  alcohol  (methyl  alcohol)  is  pro- 
duced when  wood  is  heated  in  closed  vessels  which  do  not 
permit  it  to  burn.  It  is  found  to  be  in  fact  related  to 
methane;  thence  it  is  called  methyl  alcohol,  and  to  it  is 
assigned  the  formula  CH3  OH.  It  is  viewed  as  methane,  or 
marsh  gas  (CH4),  which  has  had  the  radicle  OH  substituted 
for  one  of  the  orignal  atoms  of  hydrogen.  It  is  also  looked 


240 


CHEMISTRY. 


upon  as  formed  after  the  water  type.  From  this  point  of 
view  it  is  viewed  as  water  (H-O-H)  in  which  one  of  the 
hydrogen  atoms  has  been  replaced  by  the  compound  radicle 
methyl  (CH3)  producing  the  substance  expressible,  as  before 
stated,  by  the  formula  CH3OH. 

The  following  diagrams  illustrate  this  statement  : 


Marsh  gas. 

Methyl  alcohol. 

Methyl  alcohol. 

Water. 

r—H 

f—  H 

CH3      . 

H 

1 

c     -H 

1  H 

0 

0 

]—  H 
l-H 

L~(OH) 

II 

A 

It  has  long  been  known  that  the  sugary  juices  extracted 
from  many  vegetable  matters  are  capable  of  a  peculiar  change 
called  alcoholic  fermentation,  by  which  there  is  produced 
from  the  sugar  a  new  substance  called  alcohol  (more  strictly 
speaking,  ethyl  alcohol).  It  is  a  highly  combustible  sub- 
stance, burning  in  the  air  with  a  blue  flame  ;  when  taken  into 
the  stomach  it  produces  well-recognized  stimulating  and 
even  terribly-intoxicating  effects.  Analysis  has  shown  it  to 
possess  the  composition  expressed  by  the  formula  C2H5OH. 
It  may  be  viewed  as  ethane  (C2H5H)  in  which  one  atom  of 
hydrogen  has  been  replaced  by  the  radicle  O  H.  It  is  also 
viewed  as  formed  after  the  water  type— that  is,  it  may  be 
looked  upon  as  water  (H-O-H)  in  which  one  hydrogen  atom 
is  replaced  by  the  compound  radicle  (C2H5). 

The  following  diagrams  illustrate  this  statement : 


Ethane. 

Ethyl  alcohol. 

Ethyl  alcohol. 

Water. 

f=H 

-H 

(C,  H5) 

H 

C  1  —  H 
C  1  —  H 

0  —  O 

-H 
-H 

A 

1 
O 
I 

-H 

—  H 

jj 

H 

l-H 

I  -(OH) 

ORGANIC   CHEMISTRY.  241 

Among  the  organic  compounds  recognized  as  composed  of 
carbon,  oxygen,  and  hydrogen,  there  are  the  important  groups 
called  carbohydrates,  including  glucose,  cane  sugar,  and  woody 
fibre,  also  called  cellulose. 

Under  each  head  are  well-known  substances,  most  of  them 
valuable  as  food.  From  this,  of  course,  should  be  excluded 
woody  fibre,  or  cellulose,  although  the  cellulose  group  in- 
cludes some  of  the  most  important  food  materials,  chief 
among  which  is  starcli.  Starch  occurs  in  slightly  different 
forms  in  most  vegetable  seeds  and  grains.  This  statement 
carefully  examined  shows  that  starch  is  one  of  the  most 
important  constituents  of  the  food  of  man  as  well  as  of  the 
lower  animals.  The  millions  of  inhabitants  of  China  and 
India  live  largely  upon  rice,  whose  most  abundant  constituent 
is  starch.  Western  nations  consume  for  food  vast  quantities 
of  wheat  flour,  Indian  meal  and  potatoes,  all  of  which  contain 
large  quantities  of  starch. 

It  is  a  matter  of  common  observation  that  when  the  alcoholic 
fermentation  has  proceeded  some  time  it  is  liable  to  be  fol- 
lowed by  a  somewhat  different  kind  of  fermentation,  attended 
by  souring. 

Vinegar  is  produced  from  cider  and  wrine  in  this  way; 
vinegar  contains  a  peculiar  acid  called  acetic  acid  ;  nnd  just 
as  ethyl  alcohol  is  produced  from  cane  sugar  by  alcoholic  fer- 
mentation so  acetic  acid,  is  produced  from  ethyl  alcohol  by 
acetous  fermentation.  Acetic  acid  is  found  to  be  expressible 
by  the  formula  (C2H3O)  O  II. 

Acetic  acid  is,  however,  only  one  member  of  an  extensive 
group  of  organic  acids.  Some  of  them,  however,  are  very 
different  from  vinegar  in  their  properties;  thus  oleic,  palmitic 
and  stearic  acids  occur  in  combination  with  glycerin  in  most 
ordinary  fats.  When  separated  from  the  glycerin  they  are 
truQ  acids,  even  though  they  do  not  manifest  that  sourness 
which  is  the  ordinary  characteristic  of  acids. 

Ethers  and  aldehydes  are  organic  compounds  producible  by 
certain  transformations  of  alcohol  and  acids. 

The  four  great  classes  of  compounds  of  carbon  containing 
16 


242  CHEMISTRY. 


oxygen  and  hydrogen  just  touched  upon  have  many  repre- 
sentatives derived  from  the  many  hydrocarbons  of  the  paraf- 
fin series ;  but  it  would  be  out  of  place  to  attempt  any  further 
discussion  here. 

Sub-Chapter  II.— The  Aromatic  Series. 

This  interesting  series  includes  compounds  grouped  as  sug- 
gested by  the  table  in  Sub-Chapter  I. — that  is,  it  includes 
hydrocarbons  like  benzol  C6II6  (see  p.  249),  alcohols  like 
phenyl  alcohol  (C6H6  OH,  commonly  known  as  carbolic  acid), 
while  its  nitrogen  series  is  represented  by  phenylamine 
(CeH6  NH3  commonly  called  aniline)  which  is  the  starting- 
point  of  the  aniline  colors. 

Napthalene,  turpentine  and  other  terpenes,  belong  to  this 
general  series. 

Sub-Chapter  III.— Other  Vegetable  Matters. 
In  the  vegetable  world  chemists  recognize  a  great  number 
of  interesting  substances  not  capable  of  so  easy  a  reference 
to  the  type  compounds,  or,  indeed,  to  any  clearly-defined 
chemical  position.  That  they  are  important,  however,  ap- 
pears from  the  mere  mention  of  such  alkaloids  as  nicotin  of 
tobacco,  caffeine  of  coffee,  theine  of  tea,  morphine  of  opium, 
quinine  of  Peruvian  bark,  and  strychnine  of  the  nux  vomica 
bean,  to  which  might  be  added  many  other,  both  allied  and 
not  associated,  vegetable  matters. 

Sub-Chapter  IV.— Animal  Matters. 

The  groups  of  compounds  referred  to  in  the  preceding 
paragraphs  gradually  rise  in  the  scale  of  complexity.  Yet 
there  is  a  vast  group  of  animal  compounds  containing  vary- 
ing amounts  of  the  elementary  substances,  carbon,  hydrogen, 
oxygen,  nitrogen,  sulphur  and  phosphorus — sometimes  all  at 
once  in  the  same  molecule.  Of  course  these  are  still  more 
complex.  Among  them  may  be  mentioned  the  albuminous 
matters  occurring  in  blood  and  white  of  egg,  the  casein  of 


ORGANIC   CHEMISTRY.  243 

milk,  gelatins,  fibrins,  and  even  substances  found  in  the  brain 
and  nerves,  like  cerebrin  and  lecithin. 

Chemists  feel  certain,  however,  that  the  number  known  is 
an  exceedingly  insignificant  fraction  of  those  existing  in 
animal  and  vegetable  substances. 

Hundreds  of  observers  and  investigators  have  devoted  in 
the  aggregate  an  enormous  amount  of  study  to  the  carbon 
compounds.  At  the  present  day  the  study  of  the  c;irbon  com- 
pounds is  the  chief  business  of  chemists;  indeed,  the  present 
may  be  designated  as  the  era  of  organic  chemistry.  Yet  the 
subject  is  so  difficult  that  even  professional  chemists  are  yet 
in  a  condition  that  perhaps  ought  to  be  designated  as,  rela- 
tively, one  of  extreme  ignorance  of  the  chemistry  of  animal 
and  vegetable  substances. 

They  are  undoubtedly  making  great  strides  in  advance, 
but  the  progress  thus  far  made  seems  to  have  as  its  chief 
result  the  revealing  of  the  world-wide  field  yet  to  be  criti- 
ically  explored. 


244  CHEMISTRY. 


XXVII. 

ILLUMINATING    GAS. 

T  is  manifest,  from  what  has  been  said,  that  in  a 
book  like  the  present  it  is  impossible  to  give  any 
considerable  discussion  of  the  vast  field  offered 
by  the  organic  compounds  of  carbon.  It  seems 
better  to  choose  for  description  some  important  manufactur- 
ing operation  that  involves  these  compounds,  and  that  is  on 
other  accounts  specially  instructive.  Accordingly  the  manu- 
facture of  illuminating  gas  is  selected  for  consideration  here. 

The  Manufacture  of  Illuminating  Gas. 

The  material  on  which  this  industry  is  based  is  bituminous 
coal.  This  substance  is  clearly  a  vegetable  product,  though 
it  is  derived  from  a  vegetation  which  lived,  flourished  and 
decayed  in  a  period  of  pre-historic  antiquity. 

The  manufacture  of  illuminating  gas,  although  one  of  the 
most  important  of  the  chemical  industries  of  to-day,  had  its 
beginning  but  little  before  the  opening  of  the  present  century. 
A  Scotchman  named  William  Murdoch  is  generally  credited 
with  the  first  introduction,  into  considerable  use,  of  burning 
gas  made  from  coal.  In  1798  lie  gained  the  opportunity  to 
introduce  his  method  of  illumination  into  the  engine-works 
of  Boulton  &  Watt,  located  at  Soho,  near  Birmingham.  From 
that  date  the  manufacture  and  use  of  illuminating  gas  from 
soft  coal  has  extended  and  expanded  until  it  has  reached  its 
present  enormous  development. 

General  Principles  of  the  Process. 

The  general  principle  of  the  manufacture  is  exceedingly 
simple.  Its  commercial  growth,  however,  has  been  assisted 
by  the  invention  and  application  of  a  multitude  of  delicate 
and  ingenious  appliances. 


ILLUMINATING    GAS. 


245 


If  any  person  will  take  a  glass  test-tube,  place  in  it  a  few 
fragments  of  starch,  and  will  then  heat  the  starch  strongly 
over  a  lamp  flame,  he  will  readily  detect  three  important 
effects.  The  first  is  that  a  mass  oi  smoky  gas  or  vapor  pours 
out  of  the  mouth  of  the 'test-tube.  The  second  is  that  an 
oily  or  tarry  liquid  condenses,  on  the  inside  of  the  tube,  and 
runs  down  in  streams.  The  third  is  that  at  the  close  of  the 
operation  a  mass  of  carbon  remains  in  the  bottom  of  the  tube 
where  the  starch  was.  Now  the  various  substances  that  have 
been  referred  to  as  produced  by  the  heating  process  are  ref- 
erable to  the  decomposition  of  the  molecules  of  starch. 


Fin.  72.— Three  views  of  a  gas  retort. 

A  Similar  Operation   on  a  Large  Scale. 

In  the  manufacture  of  illuminating  gas  on  a  large  scale 
there  are  developed  practically  the  same  series  of  phenomena 
as  those  noted  in  the  experiment  with  starch  just  referred  to. 

In  the  manufacture  of  illuminating  gas,  instead  of  starch, 
as  just  described,  soft  coal  or  bituminous  coal  is  used. 

In  place  of  a  lamp  a  row  of  large  furnaces  is  employed  to 
supply  the  heat. 

Instead  of  glass  tubes  those  of  earthenware,  ten  or  twelve 
feet  in  length  and  between  one  and  two  feet  in  diameter,  are 
used.  These  tubes,  called  retorts,  are  placed  in  a  horizontal 


246 


CHEMISTRY. 


position  and  so  that  the  flame  of  the  fire  in  the  furnace  may 
sweep  around  them  and  raise  them  to  a  cherry-red  heat.  At 
the  front  end  of  the  retort  is  attached  a  door  to  prevent  the 
escape  of  the  gases  generated,  and  there  is  also  a  suitable 
pipe  to  carry  these  gases  forward  to  those  other  portions  of 
the  works  which  serve  to  perform  upon  the  crude  gas  cer- 
tain necessary  purifications;  these  are,  first,  the  condensation 
of  condensable  vapors;  second,  the  removal  of  objectionable 
gases. 

The  operations  spoken  of  show  that  the  gas  must  be  carried 
from  one  portion  of  the  establishment  to  another.     Now  illu- 


•pIG   73.— Section  showing  five  retorts  in  place. 

minating  gas  is  made  up  of  material  substances,  and,  although 
lighter  than  air,  yet  they  distinctly  possess  weight.  Gas  will 
not  move  of  itself;  to  carry  it  from  place  to  place  the  appli- 
cation of  force  by  means  of  mechanical  appliances  is  requisite. 
In  fact,  it  is  discovered  that  what  is  called  an  exhauster  is 
necessary  for  use  in  gas-works.  The  exhauster  is  simply  a 
kind  of  rotary  pump  which  pulls  the  gas  from  the  retorts  in 
which  it  is  first  formed,  and  pushes  it  along  through  the  vari- 
ous purifiers,  to  the  gas-holder  in  which  it  is  stored.  If  the 


ILLUMINATING    GAS.  247 

exhauster  were  not  used  there  would  be  a  constant  tendency 
to  the  creation  of  pressure  in  the  retort,  by  virtue  of  which 
the  gas  would  penetrate  the  earthenware  into  the  fire,  and  so 
become  a  source  of  loss. 

From  what  has  been  said  it  will  be  easily  comprehended 
that  the  essential  parts  of  a  gas-works  are  the  following  : 

First.     The  furnace. 

Second.     The  retorts,  in  which  the  coal  is  heated. 

Third.  The  hydraulic  main;  a  trough  of  water  in  which  the 
gas  is  cooled,  and  which  also  serves  as  a  gate,  through  which 
the  gas  can  pass  forward  toward  the  purifiers,  but  not  back- 
ward toward  the  retort. 

Fourth.  The  out-door  condensers,  in  which  the  gas  is  cooled 
and  some  of  its  vapors  condense  to  tarry  liquids. 

Fifth.  The  scrubber,  in  which  the  gas  is  cleansed  by  a 
spray  of  water. 

Sixth.  The  purifiers,  where  sulphuretted  hydrogen,  and 
some  other  objectionable  gases  are  removed. 

Seventh.  The  gas  holder,  in  which  the  finished  gas  is  col- 
lected and  stored  prior  to  delivery  to  consumers. 

The  processes  by  which  these  various  appliances  are  used 
in  the  manufacture  of  illuminating  gas  may  be  briefly 
sketched  as  follows: 

A  suitable  quantity  of  soft  coal  is  placed  in  an  even  layer 
on  the  bottom  of  the  retort.  Gas  at  once  forms  and  streams 
out  of  the  open  door.  The  door  of  the  retort  being  now 
quickly  closed  by  the  workman  the  gas  passes  out  through 
an  exit  pipe — called  the  dip-pipe,  because  it  dips  into  the 
water  of  the  hydraulic  main.  The  gas  bubbles  up  from  the 
dip-pipe  through  the  water.  Once  delivered  in  the  hydraulic 
main,  the  gas  cannot  go  back  to  the  retort. 

Next,  the  gas  passes  through  the  condensers,  a  series  of 
connected  up-and-down  pipes.  As  these  condensers  stand  in 
the  open  air  they  cool  the  gas  so  that  it  deposits  tarry  liquids 
that,  until  this  stage,  have  been  suspended  in  it  in  the  form 
of  vapor. 

Next  the  gas  flows  to  a  large  iron  box,  called  the  scrubber. 


248  CHEMISTRY. 


In  different  works  the  scrubber  varies  considerably  in  out- 
ward shape  and  internal  arrangements.  Its  essential  office 
however  is  to  wash  the  gas,  and  it  does  so  by  the  use  of 
water  which  is  applied  to  the  gas  either  in  sprays  or  thin 
films.  Ammonia  gas  is  the  principal  substance  absorbed  by 
the  water  in  the  scrubber.  Indeed  the  liquor  thus  produced 
is  the  main  commercial  source,  at  the  present  day,  of  am- 
monia and  its  compounds. 

The  gas  next  goes  to  the  purifiers.  These  are  large  iron 
boxes  supplied  with  a  multitude  of  shelves  upon  which,  in 
most  works,  dry  quicklime  is  spread.  The  quicklime  absorbs 
sulphuretted  hydrogen  and  some  other  acid  gases.  From 
these  purifiers  the  gas  is  carried  on  to  the  gas  holder. 

The  Distillation  of  Coal,  Chemically  Considered. 

Under  the  influence  of  the  high  temperature  of  the  gas 
furnace  the  soft  coal  in  the  retorts  undergoes  decomposition. 
As  has  before  been  intimated,  three  distinct  classes  of  sub- 
stances are  produced:  Solids,  which  are  left  in  the  retorts; 
liquids,  which  are  condensed  in  the  various  coolers;  gases, 
which  pass  on  to  the  gas  holder. 

First.  The  solids.  These  are  principally  two  kinds  of 
carbon.  One  is  coke — the  principal  solid  matter  found  in 
the  retorts  as  a  residue  from  the  soft  coal  after  the  latter  has 
ceased  to  evolve  gas.  It  is  merely  a  form  of  carbon,  some- 
what spongy  in  its  structure.  It  is  sold  for  use  as  fuel. 
Beside  this,  the  retorts  accumulate  a  sort  of  scale  of  a  very 
different  form  of  carbon  called  gns  carbon.  It  is  extremely 
hard  and  almost  non-combnstible,  being  even  very  difficult  to 
remove  from  the  retorts.  It  is  at  present  somewhat  used  in  the 
manufacture  of  the  carbon  pencils  employed  in  electric  lights 
of  the  arc  variety.  Prior  to  this  use  it  found  scarcely  any 
commercial  outlet. 

Second.  The  liquids.  The  first  condensation  of  liquids 
takes  place  in  the  hydraulic  main,  where  tarry  and  oily  mat- 
ters condense  and  accumulate,  and  are  drawn  off  from  time 


..   .      •  ,  • 


I  ..    :' 


• 


ILLUMINATING    GAS.  '249 


to  time  into  the  tar  well.  Again,  in  the  condensers  there  is 
a  still  futher  deposition  of  liquids,  also  tarry  and  oily  in 
their  nature. 

These  liquids  consist  of  very  complicated  mixtures  of  car- 
bon compounds,  but  they  are  of  the  most  interesting  char- 
acter. In  the  earlier  history  of  the  manufacture  of  coal  gas 
they  were  regarded  as  mere  nuisances.  Little  by  little,  how- 
ever, chemists  have  learned  to  separate  the  intermingled 
products,  and  have  thus  been  able  to  obtain  a  number  of 
substances  of  striking  interest  and  usefulness  in  the  arts. 
Among  the  multitudes  of  substances  that  go  to  make  up  the 
liquid  called  coal-tar,  some  are  as  yet  hardly  classified ; 
others  are  distinctly  recognized,  and  have  uses  of  great  com- 
mercial importance.  Of  these  latter,  two  will  be  mentioned 
here.  These  are  anthracene  and  benzol. 

The  substance  called  anthracene,  a  compound  of  carbon 
and  hydrogen  (C14H]0),  has  sprung  into  the  highest  commer- 
cial importance.  This  is  referable  to  the  fact  that  it  has 
been  found  to  be  a  suitable  material  from  which,  by  chemical 
processes,  there  may  be  manufactured  a  substance  known  as 
alizarin,  besides  other  equally  valuable  and  interesting  com- 
pounds. Alizarin  was  previously  recognized  as  the  coloring 
matter  of  chief  value  in  madder  root,  a  substance  that  has 
been  used  as  a  dye-stuff  for  above  a  thousand  years.  The 
alizarin,  whether  of  madder  or  from  anthracene,  is  a  coloring 
matter  of  the  highest  value  and  usefulness.  It  affords  turkey- 
red,  and  other  colors  that  are  very  important  because  they  are 
extremely  brilliant  and  extremely  fast.  Its  artificial  manu- 
facture, from  the  anthracene  of  the  filthy  and  offensive  coal- 
tar,  is  one  of  the  greatest  triumphs  of  this  or  any  age. 

Another  substance  found  in  the  coal-tar  is  benzol,  a  com- 
pound of  carbon  and  hydrogen  having  the  formula  CJIC. 
This  is  the  principal  material  from  which,  by  a  variety  of 
well-understood  though  complicated  chemical  processes,  the 
well-known  aniline  colors  have  been  produced.  While  these 
colors  may  well  command  the  admiration  of  all,  on  account 
of  their  unsurpassed  beauty  and  brilliancy,  they  are  of 


250  CHEMISTRY. 


especial  interest  to  the  scientist  by  reason  of  the  chemical 
laws  they  illustrate.  The  preparation  of  these  colors,  as  a 
group,  ranks  second  only  as  a  chemical  achievement  to  that 
of  artificial  alizarin. 

Third.  The  gaseous  products.  The  gases  generated  in 
the  process  of  the  coal-gas  manufacture  are  extremely  nu- 
merous; some  of  them  are  of  high  illuminating  power,  of 
•which  that  called  ethylene  (C2H4)  is  an  excellent  example. 
Again,  there  are  some  that  are  combustible,  but  yet  are  of 
slight  illuminating  power.  Substances  of  this  class  are  pres- 
ent in  the  finished  product.  Hydrogen  and  carbon  monoxide 
(CO)  may  serve  as  examples.  There  are  always  present  also 
gases  that  are  either  injurious  to  the  illuminating  power  or 
are  otherwise  objectionable.  For  example,  nitrogen  is 
always  present,  and  it  is  not  practicable  to  remove  it  from 
the  gas.  It  contributes  nothing  to  the  value  of  the  product. 
Again,  certain  sulphur  compounds,  like  sulphuretted  hydro- 
gen, are  usually  present.  These  indeed  burn,  but  they  give 
rise  to  offensive  and  unwholesome  oxides  of  sulphur. 

The  sketch  thus  given,  while  it  but  imperfectly  describes 
the  wonderful  industry  in  question,  with  its  various  well- con- 
trived and  delicate  nppliances,  serves,  however,  to  give  some 
idea  of  the  importance  of  the  operation  from  a  chemical 
point  of  view,  and  the  mine  of  rich  materials  its  carbon  com- 
pounds offer  to  chemical  students. 


SILICON.  251 


CLOSING  CHAPTER. 


CHAPTER    XXVIII. 

SILICON. 

|ILICON  may  well  be  considered  important  on  ac- 
count of  its'  quantity  in  the  earth,  if  on  no  other. 
In  an  earlier  chapter  it  has  been  shown  that 
oxygen  exists  in  our  globe — including  its  atmos- 
phere and  its  oceans — in  an  amount  equal  to  about  one  half 
of  the  weight  of  the  whole.  Now  silicon  exists  in  a  quantity 
equal  to  about  one  fourth  of  this  entire  weight.  In  the  solid 
earth,  however,  neither  of  these  substances  exists  in  the  un- 
combined  form.  These  facts  seem  to  involve  as  a  necessary 
consequence  that  they  exist  in  the  earth,  to  a  large  extent, 
combined  with  each  other  ;  indeed  this  is  found  to  be  the 
case.  The  principal  earthy  matter  of  our  planet  is  the  com- 
pound of  silicon  and  oxygen,  existing  either  alone,  in  the  form 
of  sand,  quartz,  rock-crystal,  and  similar  minerals,  or  else  in 
combination  with  other  well-known  abundant  earth  mate- 
rials, such  as  oxides  of  calcium,  magnesium  and  aluminium. 
It  has  already  been  stated  that  carbon  is  the  characteristic 
element  of  animal  and  vegetable  matters  ;  so  silicon  is  the 
characteristic  element  of  mineral  matters.  Thus  granite,  and 
similar  archaic  rocks,  contain  approximately  twenty-five  per 
cent,  of  silicon. 

In  nature  silicon  performs  its  important  office  as  a  con- 
stituent of  rock  material,  with  a  fitness  that  is  referable 
largely  to  the  high  degree  of  stability  possessed  by  most  of 
its  compounds.  The  permanence  of  the  materials  of  the 
earth's  surface  under  the  influence  of  heat,  water,  frost,  and 
similar  agencies,  is  an  illustration  of  this  principle. 


CHEMISTRY. 


Silicic  oxide  (SiOa),  occurs  on  our  globe  in  many  different 
forms,  of  which  diatomaceous  earth  and  rock  crystal  may  be 
mentioned. 

Diatomaceous  earth  is  a  powdery  material  found  in  abun- 
dant deposits  in  many  parts  of  the  world.  Its  characteristic 


FIG.  74.— Diatomaceous  earth  as  seen  through  the  microscope. 


structure,  when  examined  under  the  microscope,  reveals  its 
nature ;  then  it  is  seen  to  be  made  up  of  the  shells  of  minute 
vegetable  organisms  called  diatoms.  These  assume  a  great 
many  beautiful  forms,  and  some  of  them  are  checkered  all 
over  with  markings  of  such  extreme  fineness  that  they  have 


SILICON. 


253 


been  used  as  test  objects  for  trying  the  resolving  power  of  the 
objectives  of  microscopes.  This  kind  of  earth  is  employed, 
as  has  already  been  stated,  in  the  preparation  of  dynamite. 

Quartz  sometimes  occurs  in  colorless  transparent  masses  of 
great  beauty  and  clearness,  called  rock  crystal.  The  ame- 
thyst is  the  same  substance  slightly  colored  by  compounds 
of  the  metal  manganese,  while  quartz  exists  of  a  variety  of 


FIG.  75.— Mass  of  natural  quartz  crystals. 

other  shades,  in  some  of  which  it  is  prized  as  a  gem.  Quartz 
generally  assumes  forms  of  a  hexagonal  tendency ;  they 
are  often  hexagonal  prisms  terminated  by  hexagonal  pyr- 
amids. 

Quartz  and  the  finer  and  purer  varieties  of  sand  are  used 
largely  in  the  manufacture  of  glass.  The  silicic  oxide  here 
displays  what  may  be  expressed  as  its  acid  tendencies  ;  for  in 
the  manufacture  of  glass  it  is  fused  with  sodic  carbonate, 
and  then  the  silicic  oxide  displaces  the  carbon  dioxide 


254  CHEMISTRY. 


from  the  sodic  carbonate ;  as  a  result  there  is  formed 
what  must  be  regarded  as  a  true  salt,  or  a  mixture  of  salts, 
that  in  the  simplest  kind  of  glass  may  be  termed  sodic  sili- 
cate. 


Closing  Words.  The  course  laid  out  in  the  preface  is 
now  terminated  with  silicon,  as  there  planned.  From  scien- 
tific considerations,  this  is  a  natural  ending  ;  it  seems  to  be 
appropriate  on  another  account  also.  After  the  reader  has 
been  carried,  in  thought,  among  the  various  gaseous  ele- 
ments that  make  up  atmosphere  and  oceans,  it  seems  suit- 
able that  we  should  say  farewell  to  him  upon  the  discussion 
of  that  element  that  may  be  called  the  characteristic 
material  of  our  solid  earth. 


INDEX 


[THE  NUMBERS  REFER  TO  PAGES-! 


Abel,  Sir  F.  A.,  189. 
Acid,  Hydriodic,  45, 105. 

Hydrobromic,  45, 105. 

Hydrochloric,  83. 

Hydrofluoric,  105,  106. 

Nitric,  174. 

Oleic,  241. 

Palmitic,  241. 

Stearic,  241. 

Sulphuric,  32,  34,  156. 
Affinity,  Chemical,  41. 
Air,  Atmospheric,  weight  of,  1<8. 

composition  of,  178. 

fitness  for  its  uses,  182. 

not  a  compound,  182. 
Alcohol,  Ethyl,  239. 

Methyl,  239,  240. 
Alcohols,  239,  240. 
Aldehydes,  239. 
Alizarin,  249. 
Alkali  trade,  86,  88,  99. 
Allotropism,  121, 199. 
Amethyst,  253. 
Ammonia  gas,  171. 
Ampere,  101. 
Anthracene,  249. 
Atmosphere,  The,  177. 
Atom,  37,  38. 
Azote,  167. 

Bacon,  Roger,  185. 
Balard,  93. 
Balloons,  68. 

Centenary  of,  77. 

Proclamation  on,  71. 
Barilla,  100. 
Battery,  Galvanic,  58. 
Benzol,  234,  249. 
Berthollet,  86. 
Berzelius,  2%,  24. 
Beverages,  Effervescing.  231. 
Biot,  55,  73. 
Bittern,  93. 
Black,  Joseph,  57, 70. 
Bleaching,  91. 

by  sulphur,  153. 

powder,  86. 

Blowpipe,  Compound,  125. 
Bone  Coal,  208. 
Borax,  161. 
Boron,  161. 
Brandt,  195. 
Bromine,  93. 
Brougham,  Lord,  on  Cavendish,  55. 


Calcaroni,  147. 
Carbohydrates,  241. 
Carbon,  207. 

decolorizing  by,  238. 

dioxide,  227. 

gas,  248. 

infusibility  of,  220. 

monoxide,  226. 
Cavendish,  Henry,  54. 
Charcoal,  207. 

animal,  208. 
Chemistry  defined,  8. 

organic,  232. 

scope  of,  10. 
Chlorine,  79. 
Chloroform,  239. 
Coal,  211. 
Coke,  248. 

Combustion,  by  oxygen,  118,  128. 
Compound,  chemical,  idea  of,  57. 
Compounds,  11. 

binary,  29. 

ternary,  31. 
Courtois,  101. 
Cupric  nitrate,  175. 

Daguerre,  96. 

Dalton,  John,  48. 

Davy,  Humphry,  54,  81,  101. 

de  Morveau,  20. 

De  Rozier,  72. 

Despatch,  microscopic,  77. 

Diamidogen,  170. 

Diamond,  212. 

Diatoms,  252. 

Dobereiner,  63. 

Dynamite,  192. 

Earth,  composition  of,  16. 
diatomaceous,  252. 

Elements,  11. 

Equivalence,  43. 

Ethers,  239. 

Explosives,  184. 

Explosions  of  mixed  oxygen  and  hydro- 
gen, 128. 

Ferric  nitrate,  175. 
Fireworks,  187. 
Fluorine,  105. 

isolation  of,  109. 
Fluor-spar,  105. 
Fulminates,  188. 


256 


INDEX. 


Gas,  illuminating,  244. 

natural,  223. 

notion  of,  57. 
Gay-Lussac.  74,  101. 
Glaisber  and  Coxwell,  75. 
Glass,  253. 
Granite,  251. 
Graphite,  212. 
Gun-cotton,  189. 
Gunpowder,  184. 

Haiiy,  109. 

Hell  Gate  explosion,  193. 
Hydrazine,  170. 
Hydrocarbons,  fatty,  238. 
Hydrogen,  53. 

combustion  of,  65. 

diffusion  of,  63. 

dioxide,  123. 

preparation  of,  58. 

uses  of,  66. 

Ice  broken  up  by  dynamite,  193. 

machines,  173. 
Iodine,  98. 

Janssen,  77. 
Kelp,  100. 

Lampblack,  209. 
Language,  chemical,  20. 
Larderel,  164. 
Lavoisier,  20,  22,  111,  167. 
Leblanc,  101. 

process,  88,  101. 
Liebig,  94. 
Light,  calcium.  1 :7. 

Marsh  gas,  230. 
Mass,  35. 

Matches,  friction,  201. 
Matter  not  destroyed,  46. 
Mayow,  John,  113,  167. 
Mercury,  27. 
Metal  defined,  20. 
Molecule,  36. 
Montgolfier  brothers,  69. 

Names  for  substances,  33. 
Newton,  John,  193. 
Nickles,  107. 
Nitrogen,  166. 

dioxide,  174,  175. 

pentoxide,  174. 

protoxide,  174. 

tetroxide,  174. 

trioxide,  174. 
Nitroglycerin,  190. 
Nobel,  Alfred,  192. 
Nomenclature,  chemical,  33. 
Non-metal,  28. 

Oxygen,  110. 
Ozone,  119. 

Pelletier,  82. 
Petroleum,  223,  239. 


Phosphorus,  195. 

red,  198. 

Potassic  bromide,  97. 
Priestley,  Joseph,  57,  69,  111,  167. 
Puymaurin,  108. 

Quartz,  253. 

Radicles,  organic,  235. 

References,  reading,  12,  18,  25,  28,  34.  40, 

51.  67,  78,  91,  97,  104,  109,  130, 154,  160, 

165,  176,  183,  194,  206,  225. 
Respiration,  129. 
Roe,  82. 

Salt,  common,  79,  85. 

Scheele,  79,  86.  94,  106,  111,  166,  195. 

Sch  rotter,  198. 

Science  defined,  7. 

Sea-weed,  99. 

Series,  aromatic,  236,  242. 

fatty,  236. 

paraffin,  236. 
Silicates,  106. 
Silicic  oxide,  252. 
Silicon.  251. 
Soda  ash,  86,  99. 
Solvay  process,  88. 
Starch,  241. 
State,  nascent,  124. 
Substances,  compound,  29. 

construction  of,  35. 

elementary,  14,  40. 

classification  of,  26. 

list  of,  15. 

great  number  of,  10. 
Suffloni,  164. 
Sulphur,  144. 

compounds  of,  148. 

dioxide.  152. 

trioxide,  155. 

!  Sulphuretted  hydrogen,  150. 
Symbols  for  atoms,  23. 

Theory,  atomic,  48. 
Trough,  pneumatic,  57. 
Type  compounds,  236. 

Van  Helmont,  57. 
Varech,  100. 
Vinegar,  241. 
Vitriol,  oil  of,  156. 

Water,  131. 

as  affecting  climate,  136. 

as  a  solid,  135. 

as  a  working  contrivance,  138. 

circulation  of,  134. 

composition  of,  121. 
'  decomposition  of,  58. 

importance  of,  132. 

kinds  of,  139. 

rain,  140. 

river,  141. 

sea,  141. 

spring,  142. 

well,  143. 
Weights,  atomic,  15,  45. 

Zinc  nitrate,  175. 


RETURN  TO  the  circulation  desk  of  any 
University  of  California  Library 

or  to  the 

NORTHERN  REGIONAL  LIBRARY  FACILITY 
Bldg.  400,  Richmond  Field  Station 
University  of  California 
Richmond,  CA  94804-4698 

ALL  BOOKS  MAY  BE  RECALLED  AFTER  7  DAYS 

•  2-month  loans  may  be  renewed  by  calling 
(510)642-6753 

•  1-year  loans  may  be  recharged  by  bringing 
books  to  NRLF 

•  Renewals  and  recharges  may  be  made 
4  days  prior  to  due  date 

DUE  AS  STAMPED  BELOW 
JAN  06  2004 


DD20   15M  4-02 


